The unbound fraction

True hormone status Treatment Response Symptom correlation

The concentration of red blood cells per unit volume of blood.

Elevated levels (erythrocytosis/polycythemia) indicate chronic hypoxia, dehydration, polycythemia vera, high altitude adaptation, smoking, or erythropoietin-secreting tumors. Decreased levels indicate anemia from blood loss, nutritional deficiency (iron, B12, folate), hemolysis, bone marrow suppression, or chronic disease RBC count can be influenced by altitude, hydration status, pregnancy, testosterone levels, and certain medications (erythropoietin, anabolic steroids).

The concentration of hemoglobin in whole blood, reflecting oxygen-carrying capacity.

Elevated levels indicate chronic hypoxia, dehydration, polycythemia vera, high altitude, smoking, or erythropoietin-secreting tumors. Decreased levels (anemia) indicate blood loss, nutritional deficiency (iron, B12, folate), hemolysis, bone marrow suppression, chronic kidney disease, or chronic inflammation. Hemoglobin can be influenced by altitude, hydration status, pregnancy, age, ethnicity (lower in African Americans), and smoking.

The average volume of individual red blood cells, used to classify anemias into three categories: microcytic (MCV 100 fL).

Large red blood cells suggest vitamin B12 deficiency, folate deficiency, excessive alcohol use, liver disease, or certain medications. Small red blood cells suggest iron deficiency, thalassemia (an inherited blood disorder), chronic disease, or lead exposure. MCV increases slightly with age; reticulocytes (young red blood cells) are larger and can raise the number; combined deficiencies (iron plus B12) can produce a falsely normal MCV because the effects cancel each other out..

The average mass of hemoglobin per red blood cell, calculated by dividing total hemoglobin by the red blood cell count. MCH correlates closely with MCV.

Elevated levels often correspond with macrocytic anemia (larger than normal red blood cells) caused by Vitamin B12 or folate deficiency, liver disease, alcohol abuse, or an underactive thyroid. Low levels (hypochromia) typically indicate iron deficiency anemia or thalassemia, where red blood cells are smaller than normal and lack sufficient hemoglobin. MCH status can be falsely elevated by hyperlipidemia (high blood fats), very high white blood cell counts, or the presence of cold agglutinins (antibodies that cause red blood cells to clump together).

The density of hemoglobin within each red blood cell. Unlike MCH (which measures total hemoglobin mass per cell), MCHC accounts for cell size by relating hemoglobin content to cell volume.

Elevated levels (hyperchromia) are rare and physiologically limited but can indicate Hereditary Spherocytosis. Levels may also appear falsely high due to cold agglutinins (clumped cells) or lipemia (fatty blood). Low MCHC indicates hypochromic red blood cells (paler than normal when viewed under microscope). Can also indicate Iron deficiency anemia, thalassemia, anemia of chronic disease, sideroblastic anemia, lead poisoning. MCHC status can be falsely elevated by autoagglutination (cells clumping in the tube), high cholesterol/triglycerides, or hemolysis (broken cells).

The coefficient of variation of the red blood cell volume distribution, essentially measuring how consistent or inconsistent the red blood cells are in size.

Elevated levels indicate significant heterogeneity in cell size, commonly seen in early nutritional deficiencies (iron, B12, or folate) before anemia becomes overt, hemolytic anemia, liver disease, or following recent blood transfusions. Low levels indicate that red blood cells are very uniform in size; while often normal, this can also occur in chronic anemias where cells are consistently small (microcytic) or large (macrocytic) rather than mixed. RDW status can be influenced by a high reticulocyte count (immature red blood cells are larger), alcohol abuse, and the fragmentation of cells due to heart valves or severe infection.

The number of platelets per microliter of blood, assessing the body's ability to form clots and stop bleeding

Elevated levels (thrombocytosis) can indicate chronic inflammation, infection, iron deficiency anemia, removal of the spleen (splenectomy), or myeloproliferative disorders like essential thrombocythemia Low levels (thrombocytopenia) indicate a risk of excess bleeding and may result from bone marrow suppression (chemotherapy, radiation), autoimmune destruction (ITP), viral infections (Hepatitis C, HIV), or chronic liver disease. Platelet status can be influenced by recent surgery, physical exertion, acute infection (which often causes a temporary rise), and alcohol consumption (which can lower counts).

Platelet size. Larger platelets are usually younger and more active. Smaller platelets tend to be older.

Elevated levels suggest the bone marrow is rapidly producing new platelets, often seen in immune thrombocytopenia (ITP) where platelets are destroyed and replaced quickly, or in recovery from chemotherapy. Low levels indicate older average platelets, typically seen when the bone marrow is underproducing (aplastic anemia) or suppressed by cytotoxic drugs. MPV status can be influenced by the time between blood draw and analysis (platelets swell in EDTA tubes over time) and cardiovascular risk factors like obesity and diabetes.

The sum of all cholesterol carried in lipoproteins: LDL (low-density lipoprotein), HDL (high-density lipoprotein), and VLDL (very low-density lipoprotein).

Elevated levels may indicate familial or polygenic hypercholesterolemia, diet high in saturated/trans fats, hypothyroidism, nephrotic syndrome, primary biliary cirrhosis, obstructive liver disease, or diabetes mellitus. Low levels may indicate hyperthyroidism, severe liver disease, malnutrition, malabsorption, chronic anemia, sepsis, critical illness, inflammatory conditions, or inherited disorders (abetalipoproteinemia, hypobetalipoproteinemia, Tangier disease). Cholesterol may be influenced by both Testosterone and Estrogen levels.

The concentration of cholesterol carried within high-density lipoprotein particles.

Elevated levels are desirable and are associated with a reduced risk of heart disease and stroke ("cardioprotective"). Low levels may indicate sedentary lifestyle, obesity, smoking, type 2 diabetes, metabolic syndrome, insulin resistance, hypertriglyceridemia, chronic kidney disease, malnutrition, certain medications (beta-blockers, anabolic steroids, progestins), or genetic conditions. Cholesterol may be influenced by both Testosterone and Estrogen levels.

The amount of fat circulating in the bloodstream.

Elevated levels may indicate excess caloric intake (especially refined carbohydrates and alcohol), obesity, poorly controlled diabetes mellitus, metabolic syndrome, hypothyroidism, nephrotic syndrome, chronic kidney disease, primary biliary cirrhosis, or familial hypertriglyceridemia. Low levels may indicate malnutrition, malabsorption, hyperthyroidism, abetalipoproteinemia, or very low-fat diets. Low triglycerides are generally not clinically concerning. Inadequate fasting is the most common cause of spuriously elevated results.

The cholesterol content within LDL particles. Most commonly calculated using the Friedewald equation (Total Cholesterol − HDL-C − Triglycerides/5).

Elevated levels may indicate familial hypercholesterolemia, polygenic hypercholesterolemia, diet high in saturated/trans fats, hypothyroidism, nephrotic syndrome, obstructive liver disease, diabetes mellitus, obesity, or medications (thiazides, cyclosporine, glucocorticoids). Low levels may indicate hyperthyroidism, malnutrition, malabsorption, severe liver disease, sepsis, critical illness, or inherited disorders (abetalipoproteinemia, hypobetalipoproteinemia). Nonfasting samples may underestimate LDL

The proportion of total cholesterol relative to HDL cholesterol.

Elevated ratio may indicate low HDL cholesterol, elevated LDL or VLDL cholesterol, or a combination. Conditions associated with elevated ratio include metabolic syndrome, obesity, diabetes, sedentary lifestyle, smoking, and familial dyslipidemias. An unfavorable ratio signals increased cardiovascular risk even when individual lipid values appear borderline. Low ratio may indicate high HDL (exercise, genetic factors, moderate alcohol intake) relative to total cholesterol, or very low LDL from aggressive lipid-lowering therapy. Calculated from total cholesterol and HDL values; accuracy depends on accuracy of component measurements.

The proportion of LDL cholesterol relative to HDL cholesterol.

Elevated ratio may indicate elevated LDL, low HDL, or both. Associated with increased atherogenic burden and cardiovascular risk. Conditions elevating this ratio mirror those affecting its components: familial hypercholesterolemia, metabolic syndrome, diabetes, obesity, hypothyroidism, sedentary lifestyle, smoking. Low ratio may indicate well-controlled LDL (through lifestyle or medication), naturally high HDL, or both. Calculated from LDL and HDL values. When triglycerides exceed calculation thresholds for LDL, the ratio becomes unreliable unless direct LDL measurement is used.

Represents the total cholesterol content of all atherogenic lipoproteins: LDL, VLDL, IDL, and lipoprotein(a).

Elevated levels may indicate elevated LDL, elevated VLDL (often from hypertriglyceridemia), elevated IDL, elevated lipoprotein(a), or combinations thereof. Associated conditions parallel those affecting LDL: familial hyperlipidemia, metabolic syndrome, diabetes, obesity, hypothyroidism, nephrotic syndrome, and atherogenic diets. Low levels may indicate hyperthyroidism, malnutrition, malabsorption, severe liver disease, or aggressive lipid-lowering therapy. Calculated from total cholesterol and HDL; accuracy depends on component measurements.

Serum LDL-P concentration reflects the total number of apoB-containing LDL particles per liter, with each particle containing exactly one apolipoprotein B molecule, providing a direct measure of atherogenic particle burden that may identify cardiovascular risk even when LDL cholesterol appears normal.

Elevated levels may indicate increased atherosclerotic cardiovascular disease risk, insulin resistance, metabolic syndrome, familial hypercholesterolemia, or discordance between LDL-C and true atherogenic burden. Low levels are generally favorable and associated with reduced cardiovascular risk. LDL-P can be influenced by diet, triglyceride levels, insulin resistance, medications (statins, fibrates, niacin), thyroid function, and genetic factors affecting lipid metabolism.

Average HDL particle diameter reflects the predominant stage of HDL particle maturation, with larger particles typically indicating greater cholesterol ester content and more advanced reverse cholesterol transport capacity.

Larger HDL particles may reflect more mature, cholesterol-enriched particles, though clinical significance varies. HDL particles may indicate nascent, less mature particles or impaired HDL maturation. HDL size can be influenced by exercise, alcohol consumption, triglyceride levels, genetic factors (CETP activity), and medications.

Serum concentration of large HDL particles reflects the population of fully matured HDL capable of delivering cholesterol to the liver for excretion.

Higher concentrations of large HDL particles may reflect efficient reverse cholesterol transport and favorable lipid metabolism. Reduced large HDL-P may indicate impaired HDL maturation or accelerated HDL catabolism. Large HDL-P can be influenced by exercise, alcohol consumption, and lipid-modifying medications.

Serum concentration of large VLDL particles reflects hepatic triglyceride secretion and the population of triglyceride-rich lipoproteins that may contribute to cardiovascular risk through remnant formation.

Elevated large VLDL-P may indicate insulin resistance, metabolic syndrome, or elevated cardiovascular risk from atherogenic remnant particles. Lower concentrations are generally favorable. Large VLDL-P can be influenced by dietary intake (particularly refined carbohydrates and alcohol), fasting status, insulin sensitivity, and lipid-modifying medications.

Serum LDL-P concentration reflects the total number of apoB-containing LDL particles per liter, with each particle containing exactly one apolipoprotein B molecule, providing a direct measure of atherogenic particle burden that may identify cardiovascular risk even when LDL cholesterol appears normal.

Elevated levels may indicate increased atherosclerotic cardiovascular disease risk, insulin resistance, metabolic syndrome, familial hypercholesterolemia, or discordance between LDL-C and true atherogenic burden. Low levels are generally favorable and associated with reduced cardiovascular risk. LDL-P can be influenced by diet, triglyceride levels, insulin resistance, medications (statins, fibrates, niacin), thyroid function, and genetic factors affecting lipid metabolism.

Average LDL particle diameter reflects the predominant phenotype of circulating LDL, with smaller, dense LDL (pattern B) traditionally associated with elevated cardiovascular risk, though this relationship becomes less predictive after accounting for total LDL particle number.

Larger particle size (>21.2 nm) is generally associated with pattern A phenotype and considered more favorable, though particle number remains the stronger predictor of cardiovascular events. Smaller particle size (<20.5 nm) indicates pattern B phenotype, often associated with insulin resistance, elevated triglycerides, and metabolic syndrome. LDL size can be influenced by triglyceride levels, insulin resistance, dietary carbohydrate intake, genetic factors, and medications affecting lipid metabolism.

Serum concentration of small LDL particles reflects the atherogenic subset of LDL particles that may penetrate arterial walls more readily, though this metric's independent predictive value diminishes when total LDL-P is taken into account.

Elevated levels may indicate insulin resistance, metabolic syndrome, elevated triglycerides, or pattern B LDL phenotype associated with cardiovascular risk. Lower concentrations of small LDL particles are generally favorable. Small LDL-P can be influenced by dietary carbohydrate intake, triglyceride levels, insulin sensitivity, weight status, and lipid-modifying medications.

Average VLDL particle diameter reflects the triglyceride content and metabolic processing status of these particles, with larger VLDL particles typically containing more triglycerides.

Larger VLDL particles may indicate elevated hepatic triglyceride secretion, often associated with insulin resistance or metabolic syndrome. Smaller VLDL particles may reflect lower triglyceride content or efficient lipolysis. VLDL size can be influenced by dietary fat and carbohydrate intake, fasting status, insulin sensitivity, alcohol consumption, and lipid-modifying medications.

Serum homocysteine concentration reflects the efficiency of methionine metabolism and serves as a functional marker of B-vitamin status (B6, B12, folate), with elevations indicating pathway impairment.

Elevated levels may indicate B6, B12, or folate deficiency, MTHFR gene polymorphisms, chronic kidney disease, hypothyroidism, or elevated cardiovascular and cerebrovascular disease risk. Low homocysteine is generally not clinically concerning. Homocysteine status can be influenced by B-vitamin intake, renal function, age (increases with age), coffee consumption, certain medications, MTHFR polymorphisms, creatine intake, and dietary methionine intake.

Serum Apo A-1 concentration reflects the protein component responsible for HDL's atheroprotective functions, including cholesterol efflux from peripheral tissues and delivery to the liver for excretion.

Higher Apo A-1 levels are generally associated with favorable cardiovascular profiles; very high levels may occur with familial hyperalphalipoproteinemia, estrogen therapy, or statin use. Low levels may indicate increased cardiovascular disease risk, Tangier disease (rare genetic HDL deficiency), familial hypoalphalipoproteinemia, liver disease, nephrotic syndrome, uncontrolled diabetes, or smoking. Apo A-1 status can be influenced by sex (higher in females), exercise (increases levels), alcohol consumption, smoking (decreases levels), estrogen status, and lipid-modifying medications.

Serum Apo B concentration represents the total number of potentially atherogenic particles in circulation, providing a single measurement that captures all particles capable of penetrating arterial walls and initiating atherosclerosis.

Elevated levels indicate increased atherogenic particle burden and cardiovascular risk, familial hypercholesterolemia, metabolic syndrome, or type 2 diabetes; superior to LDL-C for risk assessment when discordance exists. Low levels are generally favorable; very low levels may occur with hypobetalipoproteinemia or abetalipoproteinemia (rare genetic disorders). Apo B status can be influenced by diet, weight status, insulin resistance, statin therapy (decreases levels), and genetic factors affecting lipoprotein metabolism.

This ratio reflects the balance between pro-atherogenic and anti-atherogenic lipoproteins, with higher ratios indicating greater atherogenic potential and lower ratios indicating more favorable lipid profiles.

Elevated Apo B/Apo A-1 ratio indicates unfavorable balance between atherogenic and protective lipoproteins, associated with increased cardiovascular disease risk and abdominal aortic aneurysm risk. Lower ratios are associated with reduced cardiovascular risk. This ratio can be influenced by lifestyle factors, medications, and genetic factors affecting both Apo B and Apo A-1 metabolism; may detect risk 20 years before cardiovascular events.

The general level of inflammation in the body, specifically used to assess cardiovascular risk.

Elevated levels in the cardiovascular risk range (>3.0 mg/L) may indicate increased cardiovascular event risk, residual inflammatory risk despite statin therapy, metabolic syndrome, or chronic low-grade inflammation; values >10 mg/L suggest acute infection, injury, or active inflammatory disease. Low levels (<1.0 mg/L) are associated with lower cardiovascular risk. hs-CRP can be influenced by acute infections, chronic inflammatory conditions (rheumatoid arthritis, IBD), obesity, smoking, diabetes, estrogen therapy, or statin use (decreases levels.

Sodium concentration in blood, reflecting the balance between sodium intake, fluid intake, and kidney excretion.

Elevated levels (hypernatremia) almost always indicate dehydration (loss of free water) or high salt intake; rare causes include diabetes insipidus or kidney dysfunction. Low levels (hyponatremia) can be caused by overhydration, diuretic use, heart failure, liver disease, or hormonal imbalances. Sodium and water balance are tightly linked. Changes in sodium concentration usually reflect fluid balance rather than true sodium deficiency or excess.

The concentration of potassium in the blood.

Elevated levels (hyperkalemia) are dangerous and can cause cardiac arrhythmias; causes include kidney failure, cell damage (burns/trauma), or certain blood pressure medications (ACE inhibitorsARBs, potassium-sparing diuretics, beta-blockers). Low levels (hypokalemia) can cause muscle weakness and heart palpitations; common causes are diuretic use, chronic diarrhea, or vomiting. Potassium levels can be falsely elevated if the blood sample is "hemolyzed" (red blood cells burst during the draw), releasing their potassium into the serum.

Chloride concentration in blood.

Elevated levels (hyperchloremia) often mimic sodium elevations (dehydration) or can indicate metabolic acidosis (loss of bicarbonate). Low levels (hypochloremia) are frequently caused by prolonged vomiting (loss of stomach acid/HCl) or metabolic alkalosis. Chloride levels generally mirror sodium levels; if sodium goes up, chloride usually follows.

The acid-base status of your blood

Elevated levels typically indicate metabolic alkalosis (too much base), often due to severe vomiting or lung diseases that cause CO2 retention (like COPD). Low levels indicate metabolic acidosis (too much acid), which can be seen in kidney disease, diabetic ketoacidosis, or toxicity (aspirin/methanol).

The total amount of calcium in the blood, including both the free (ionized) calcium and calcium bound to proteins like albumin.

Elevated levels (hypercalcemia) are most commonly caused by hyperparathyroidism (overactive parathyroid glands) or malignancy (cancer). Low levels (hypocalcemia) can result from Vitamin D deficiency, kidney failure, hypoparathyroidism, or low albumin levels. Since much of the calcium is carried by albumin, low protein levels can make calcium appear low even if the active (ionized) calcium is normal.

The total concentration of testosterone in blood, reflecting testicular function in men and ovarian/adrenal androgen production in women.

Low levels may indicate primary hypogonadism (testicular failure from Klinefelter syndrome, testicular injury, infection, chemotherapy, or radiation), secondary hypogonadism (pituitary or hypothalamic dysfunction from tumors, Kallmann syndrome, or hyperprolactinemia), or late-onset/adult-onset hypogonadism associated with aging, obesity, type 2 diabetes, or chronic illness. Elevated levels may indicate androgen-secreting tumors of the adrenal glands or testes, congenital adrenal hyperplasia, hyperthyroidism (which increases SHBG and may elevate total testosterone), or exogenous androgen use (testosterone replacement therapy, anabolic steroids). In women, elevated testosterone suggests polycystic ovary syndrome (PCOS), ovarian tumors, adrenal tumors, or congenital adrenal hyperplasia. Immunoassays (what most clinics use) are prone to cross-reactivity with structurally similar steroids and can produce results that are 20% lower or up to five-fold higher than actual values, particularly at low concentrations found in women, children, and hypogonadal men. LC-MS/MS separates testosterone from similar compounds before quantifying it by molecular mass, eliminating interference and providing reliable results across the entire measurable range.

The actual amount of "bioavailable" hormone currently ready to work on the body's tissues (muscle, brain, libido).

Elevated levels often indicate exogenous testosterone use (TRT), where the sheer volume of hormone saturates the carrier proteins, leaving more floating free. In women, it is a key marker for Polycystic Ovary Syndrome (PCOS). Low levels are the most accurate indicator of true hypogonadism (Low T symptoms). A man can have "normal" Total Testosterone but feel terrible because high SHBG (a carrier protein) is locking it all up, leaving his Free Testosterone critically low. Specimen collection should occur in early morning. Different methods produce different reference ranges that are not directly comparable.

The serum concentration of DHEA-S, reflecting adrenal androgen production and functional adrenal reserve.

Elevated levels in women can cause acne, hair loss, and facial hair growth (PCOS); in men, it typically causes no symptoms but may indicate adrenal tumors. Low levels are associated with aging ("adropause"), adrenal insufficiency, low libido, fatigue, and depression. DHEA-S status can be influenced by age (declines annually after age 30), sex, chronic stress, insulin resistance, and medications including corticosteroids and insulin sensitizers.

he capacity of the blood to bind sex hormones; this determines how much of your total testosterone is actually free to work.

Elevated levels result in less free testosterone; causes include hyperthyroidism, liver disease, low-protein diets, estrogen therapy and aging. Low levels result in more free testosterone but faster clearance; causes include obesity, Type 2 diabetes, hypothyroidism, and high-sugar diets, or androgen use. SHBG status can be influenced by thyroid function, insulin sensitivity, liver health, estrogen/androgen balance, medications, and genetic polymorphisms.

The total concentration of prostate-specific antigen in serum, including both free and protein-bound fractions.

Elevated levels may indicate Benign Prostatic Hyperplasia (BPH), infection (prostatitis), or prostate cancer. TRT can cause mild elevations. Low levels are normal; however, 5-alpha reductase inhibitors (Finasteride/Dutasteride) artificially lower results by ~50%. PSA status can be influenced by age, prostate volume, medications (5-alpha reductase inhibitors), recent sexual activity, prostate manipulation, and infection or inflammation.

The serum concentration of estradiol (E2) with high precision across the full physiological range, including the low levels found in men, children, and postmenopausal women.

High levels in men cause gynecomastia, fluid retention, and emotional volatility; in women, it indicates the ovulation phase or estrogen dominance. Low levels in men cause joint pain, osteoporosis, and low libido; in women, it indicates menopause or amenorrhea, and also osteoporosis.. Estradiol status can be influenced by body fat percentage, liver function, aromatase activity, medications (aromatase inhibitors, SERMs), menstrual cycle phase in premenopausal women, and time of day.

The serum concentration of luteinizing hormone, reflecting pituitary gonadotropin output in response to GnRH stimulation and gonadal feedback.

Elevated levels indicate Primary hypogonadism (testicular failure, premature ovarian insufficiency), menopause, polycystic ovary syndrome (PCOS—elevated LH:FSH ratio), Klinefelter syndrome, or anorchia. Low levels indicate Secondary (central) hypogonadism, pituitary or hypothalamic dysfunction, hyperprolactinemia, anabolic steroid use, severe illness or stress, excessive exercise. LH status can be influenced by pulsatile secretion (single measurements may not reflect true baseline), menstrual cycle phase (midcycle surge), medications (GnRH agonists/antagonists, opioids), and time of day.

The serum concentration of follicle-stimulating hormone, reflecting pituitary gonadotropin output and gonadal feedback status.

High levels indicate primary hypogonadism (ovarian failure, testicular failure), menopause, diminished ovarian reserve, Klinefelter syndrome, Turner syndrome, premature ovarian insufficiency. Low levels indicate secondary (central) hypogonadism, pituitary or hypothalamic dysfunction, hyperprolactinemia, anabolic steroid use, severe illness, excessive exercise, PCOS (relatively low compared to LH). FSH status can be influenced by menstrual cycle phase, age, medications (oral contraceptives, GnRH modulators), and pulsatile secretion.

The serum concentration of progesterone with high specificity, reflecting corpus luteum function, ovulatory status, or pregnancy maintenance. The ultrasensitive method avoids cross-reactivity with DHEA and other steroids that can cause falsely elevated immunoassay results,

High levels indicate ovulation confirmed (luteal phase), pregnancy, ovarian cysts, congenital adrenal hyperplasia, certain ovarian tumors. Low levels can indicate anovulation, luteal phase deficiency (associated with recurrent miscarriage), threatened miscarriage, ectopic pregnancy. Progesterone status can be influenced by menstrual cycle timing, medications (progestins, fertility treatments), and adrenal function.

Serum IGF-1 concentration reflects integrated growth hormone secretion over time, as IGF-1 has a longer half-life and more stable levels than pulsatile GH, making it the preferred marker for assessing GH axis status.

Elevated levels may indicate acromegaly (GH-secreting pituitary tumor), excessive GH replacement therapy, or gigantism in children; very high levels require evaluation for underlying GH excess. Low levels may indicate growth hormone deficiency (childhood or adult-onset), pituitary dysfunction, malnutrition, anorexia, liver disease, or uncontrolled diabetes; levels below the 2.5th percentile for age (Z-score < -2) suggest GH deficiency. IGF-1 status can be influenced by age (peaks in adolescence, declines thereafter), nutritional status, liver function, obesity (may paradoxically lower levels), thyroid status, and medications.

The concentration of all white blood cells reflecting overall immune system activity.

Elevated levels (leukocytosis) indicate infection, inflammation, physical or emotional stress, tissue damage, allergic reactions, corticosteroid use, or hematologic malignancy. Decreased levels (leukopenia) indicate bone marrow suppression, viral infection, autoimmune disease, overwhelming sepsis, or medication effects (chemotherapy, certain antibiotics). WBC counts can be influenced by time of day, exercise, pregnancy, smoking, ethnicity (lower baseline in individuals of African and Middle Eastern descent), and splenectomy.

How many neutrophils are available to fight infection. Calculated by multiplying total white blood cell count by the percentage of neutrophils.

Elevated levels (neutrophilia) typically indicate an active bacterial infection, acute stress (physical or emotional), tissue necrosis (such as from a heart attack or burn), or chronic inflammation (like rheumatoid arthritis). Medications such as corticosteroids can also cause significant elevation. Low levels (neutropenia) indicate a weakened immune system and increased susceptibility to infection. This can be caused by viral infections (like flu or hepatitis), autoimmune disorders, chemotherapy, severe vitamin deficiencies (B12/folate), or bone marrow failure. Neutrophil status can be influenced by recent intense exercise, smoking, pregnancy, and "demargination" (where stress causes cells sticking to blood vessel walls to release into the stream, temporarily raising the count).

The actual number of lymphocyte cells per microliter of blood, derived by multiplying the total white blood cell count by the percentage of lymphocytes

Elevated levels (lymphocytosis) typically indicate an acute viral infection (such as Epstein-Barr/Mono, Cytomegalovirus, or Hepatitis), chronic bacterial infections (like Pertussis), or chronic lymphocytic leukemia (CLL). Low levels (lymphopenia) indicate a compromised immune system, often caused by corticosteroid use, severe stress (trauma/surgery), malnutrition (zinc deficiency), autoimmune lupus, HIV infection, or following radiation therapy. Lymphocyte status can be heavily influenced by stress (which lowers counts rapidly via cortisol), fasting or malnutrition, and recent intense physical exercise (which can transiently elevate counts).

The actual number of monocyte cells per microliter of blood, derived by multiplying the total white blood cell count by the percentage of monocytes.

Elevated levels (monocytosis) often indicate a chronic infection (such as tuberculosis or subacute bacterial endocarditis), recovery from an acute infection, autoimmune disease (like lupus or rheumatoid arthritis), or certain blood disorders (like chronic myelomonocytic leukemia). Low levels (monocytopenia) are rare in isolation but can occur during acute stress, severe infection (sepsis), or bone marrow suppression from chemotherapy or hairy cell leukemia. Monocyte status can be influenced by chronic inflammatory conditions and is often elevated during the recovery phase of an acute infection ("the cleanup crew" coming in after the neutrophils).

The actual number of Eosinophils cells per microliter of blood.Calculated by multiplying total white blood cell count by the percentage of eosinophils.

Elevated levels (eosinophilia) most commonly indicate an allergic reaction (asthma, hay fever, drug allergy) or a parasitic infection (worms). It can also be seen in certain autoimmune diseases (vasculitis), adrenal insufficiency (Addison’s disease), or Hodgkin lymphoma. Low levels (eosinopenia) are associated with Cushing's syndrome (excess cortisol), acute bacterial infections, sepsis, corticosteroid use, stress response. Eosinophil status exhibits a diurnal variation (counts are lower in the morning due to higher cortisol levels) and can be significantly elevated by eczema or asthma flares.

The actual number of basophil cells per microliter of blood. Calculated by multiplying total white blood cell count by the percentage of basophils.

Elevated levels (basophilia) are uncommon but can indicate chronic inflammation (ulcerative colitis), hypothyroidism, or myeloproliferative neoplasms (like chronic myeloid leukemia or polycythemia vera). Low levels (basopenia) are generally not clinically significant because the normal range includes zero, but can be associated with acute allergic reactions (where they degranulate and disappear from view) or hyperthyroidism. Basophils show diurnal variation where they are lowest in the morning and highest at night. Basophilia rarely occurs in isolation; it usually accompanies eosinophilia or other white blood cell abnormalities

The relative percentage of neutrophils compared to the total number of white blood cells in circulation.

Elevated levels (relative neutrophilia) typically indicate an active bacterial infection, acute inflammation (such as appendicitis or rheumatic fever), tissue necrosis (heart attack, burns), or significant physical or emotional stress. Low levels (relative neutropenia) are often seen in viral infections (flu, hepatitis), where lymphocytes increase and "crowd out" the neutrophil percentage, or in bone marrow suppression from chemotherapy or radiation. Neutrophil percentage can be temporarily elevated by "demargination," where stress or exercise causes cells sticking to vessel walls to release into the bloodstream, and by corticosteroid use.

The percentage of the total white blood cell count that consists of lymphocytes.

Elevated levels (relative lymphocytosis) are most commonly caused by viral infections (such as Mono, Flu, or Hepatitis), but can also indicate chronic bacterial infections or lymphocytic leukemia. Low levels (relative lymphopenia) typically occur when neutrophils are elevated (due to bacterial infection or stress), or can result from steroid use, autoimmune disorders like lupus, or HIV infection. Lymphocyte percentage is inversely related to neutrophil percentage

The percentage of the total white blood cell count that consists of monocytes.

Elevated levels (relative monocytosis) often indicate the recovery phase of an acute infection, chronic inflammatory diseases, tuberculosis, or viral infections like measles or mumps. Low levels are generally not clinically significant in isolation but can occur during acute stress or severe infection. Can also appear low if other white cell types are elevated. Monocyte percentage often rises as neutrophil levels fall during recovery from an illness.

The percentage of the total white blood cell count that consists of eosinophils.

Elevated levels (relative eosinophilia) strongly suggest an allergic response (asthma, hay fever, drug allergy) or a parasitic infection. Low levels are difficult to detect due to the low baseline but may be caused by acute stress or corticosteroid use. osinophil percentage typically follows a daily rhythm, being lower in the morning when cortisol levels are higher.

The percentage of the total white blood cell count that consists of basophils.

Elevated levels (relative basophilia) are rare but can be seen in chronic inflammation, hypothyroidism, or certain bone marrow disorders. A reading of 0% is common on routine blood tests and rarely concerning because basophils are so few in number, but can be caused due to acute infections, severe allergic reactions (anaphylaxis), hyperthyroidism, corticosteroid use, or acute stress Basophils show diurnal variation, meaning lowest in the morning, highest at night. Basophilia rarely occurs alone; it usually accompanies eosinophilia or other white cell abnormalities.

How well your kidneys are filtering waste from your blood. Rising BUN suggests kidneys may not be removing waste efficiently.

Elevated levels (azotemia) typically indicate impaired kidney function, dehydration, a high-protein diet, gastrointestinal bleeding, or heart failure (due to reduced blood flow to the kidneys). Low levels are less common but can be seen in severe liver disease (where the liver cannot make urea), malnutrition (low protein intake), or overhydration. BUN status can be influenced by diet (high protein increases it) and hydration (dehydration concentrates it, raising the number).

Kidney filtration function. Creatinine is freely filtered by the kidneys and not reabsorbed, making it a more stable marker of kidney function than BUN.

Elevated levels indicate that the kidneys are not filtering waste efficiently, suggesting kidney damage, failure, or blockage (kidney stones, prostate enlargement). Low levels are generally not a health concern but are typically associated with low muscle mass (common in elderly patients) or severe malnutrition. Creatinine status can be influenced by muscle mass (bodybuilders naturally have higher baselines) and certain supplements (like creatine monohydrate), which can artificially elevate levels without kidney damage.

The actual flow rate of filtered fluid through the kidney, serving as an overall index of kidney function.

Significantly high levels can occur in early pregnancy or early stages of diabetes (hyperfiltration), and in those with high protein intakes. Low levels indicate reduced kidney function; chronic kidney disease. eGFR is an estimate and may be less accurate in people with very high or very low muscle mass

Whether kidney abnormalities are due to reduced blood flow to the kidneys (prerenal), intrinsic kidney damage (renal), or obstruction after the kidneys (postrenal).

Elevated ratios (>20:1) typically suggest dehydration, heart failure, or GI bleeding (where BUN rises disproportionately to creatinine). Low ratios may indicate liver disease or malnutrition (low urea production) or rhabdomyolysis (muscle breakdown causing high creatinine). This ratio helps differentiate between dehydration (high ratio) and actual kidney disease (normal ratio with both markers elevated).

Overall protein status, reflecting liver synthetic function, nutritional status, and immune system activity.

Elevated levels can indicate chronic inflammation or infection (high globulins) like Hepatitis C or HIV, or bone marrow disorders like Multiple Myeloma. Low levels often signal liver disease (reduced production), kidney disease (loss through urine), or malnutrition/malabsorption. Dehydration can falsely elevate total protein by concentrating the blood.

The concentration of albumin, serving as a primary marker of liver synthetic function and nutritional status.

Elevated levels are almost exclusively caused by dehydration (hemoconcentration). Low levels indicate liver disease (cirrhosis), kidney syndrome (nephrotic syndrome), chronic inflammation, or severe malnutrition. Albumin has a long half-life (~20 days), so it reflects chronic rather than acute nutritional status.

Immune system activity and certain aspects of liver function. The calculated difference between Total Protein and Albumin.

Elevated levels often indicate chronic infection, autoimmune disease (Lupus, RA), or malignancies like Multiple Myeloma. Low levels can be a sign of renal disease or immune deficiency. Globulin is not usually measured directly but calculated; specific electrophoresis is needed to determine exactly which globulin fraction is high.

The balance between albumin and globulin production, reflecting liver function, immune activity, and overall protein status.

High ratios may indicate underproduction of immunoglobulins (hypogammaglobulinemia), certain leukemias, genetic immunodeficiencies, severe dehydration with high albumin. Low ratios suggest either low albumin (liver disease) or high globulin (chronic inflammation/infection), often serving as a nonspecific marker for systemic illness.

Liver function, bile duct patency, and red blood cell breakdown. Total bilirubin includes unconjugated (indirect) and conjugated (direct) forms.

Elevated levels (jaundice) indicate liver damage (hepatitis, cirrhosis), bile duct obstruction (gallstones), or excessive breakdown of red blood cells (hemolysis). Low levels are generally not a clinical concern. Gilbert syndrome affects 3–7% of the population and causes isolated, mild unconjugated hyperbilirubinemia that increases with fasting or illness but requires no treatment.

The activity of the ALP enzyme in the blood, reflecting liver and biliary tract function, as well as bone activity.

Elevated levels typically indicate bile duct obstruction (cholestasis) or active bone formation/turnover (such as in growing children, bone fractures, or Paget's disease). Low levels are rare but can indicate malnutrition (zinc/magnesium deficiency) or a genetic condition called hypophosphatasia. Elevated ALP requires determining whether the source is liver or bone.

The level of AST enzyme, serving as a marker for cellular injury.

Elevated levels indicate liver damage (hepatitis, alcohol abuse, cirrhosis) or muscle damage (strenuous exercise, injury). Low levels are not clinically significant but can be associated with Vitamin B6 deficiency. Intense exercise can cause significant spikes in AST without liver disease.

Liver cell (hepatocyte) injury. When liver cells are damaged, ALT leaks into the bloodstream.

Elevated levels are a direct indicator of liver cell damage, commonly seen in fatty liver disease, hepatitis, alcohol abuse, or drug toxicity. Low levels are generally normal. ALT can be mildly elevated from vigorous exercise.

The amount of sugar circulating in your bloodstream. Fasting glucose reflects baseline blood sugar when you haven't eaten for at least 8 hours.

Elevated levels (hyperglycemia) most commonly indicate diabetes (Type 1 or Type 2) or pre-diabetes, but can also be caused by acute stress, pancreatitis, hyperthyroidism, or corticosteroid use. Low levels (hypoglycemia) can result from excessive insulin dosage (in diabetics), starvation, liver disease, adrenal insufficiency, or rare insulin-secreting tumors (insulinomas). Blood glucose fluctuates throughout the day based on food intake, physical activity, and stress. Medications including corticosteroids, thiazides, beta-blockers, and certain psychiatric drugs can raise glucose levels.

The amount of insulin circulating in the blood while fasting.

Elevated levels (hyperinsulinemia) are the earliest warning sign of insulin resistance and pre-diabetes, often rising years before blood sugar (glucose) or A1C become abnormal. The pancreas is "shouting" to keep blood sugar stable. Low levels indicate that the pancreas is struggling to produce enough insulin (Type 1 Diabetes or late-stage Type 2 Diabetes). Being in a non fasted state alters insulin levels.

Your average blood sugar level over the past 2–3 months.

Elevated levels indicate chronic high blood sugar, significantly increasing the risk of cardiovascular disease, nerve damage, kidney failure, and vision loss. Low levels are rare but can indicate recent severe blood loss, chronic anemia, or liver disease. Results can be misleading in people with anemia or recent blood transfusions.

The concentration of uric acid in the blood.

Elevated levels may indicate gout or gouty arthritis, uric acid kidney stones, metabolic syndrome, chronic kidney disease, conditions with increased cell turnover (leukemia, lymphoma, chemotherapy), excessive dietary purine intake, diuretic use, dehydration, or cardiovascular disease risk. Low levels may indicate Wilson's disease, Fanconi syndrome, certain medications (high-dose aspirin, allopurinol, probenecid), severe liver disease, high-dose vitamin C supplementation, malnutrition with low purine/protein intake, or rare genetic disorders affecting purine metabolism. Uric acid status can be influenced by age, sex, body weight, alcohol consumption, fructose intake, kidney function, certain medications (thiazide diuretics, cyclosporine), recent dietary purine consumption, and genetic factors.

Serum total cortisol concentration reflects both protein-bound (~90–95%) and free cortisol, with levels exhibiting pronounced diurnal variation where it is highest in early morning and declining throughout the day.

Elevated levels may indicate Cushing syndrome (adrenal adenoma, carcinoma, pituitary ACTH-secreting tumor, or ectopic ACTH production), acute physiological stress, obesity, depression, hyperthyroidism, or exogenous corticosteroid use. Low levels may indicate primary adrenal insufficiency (Addison disease), secondary adrenal insufficiency (pituitary dysfunction), tertiary insufficiency (hypothalamic dysfunction), or abrupt discontinuation of chronic corticosteroid therapy. Cortisol levels can be influenced by collection time (diurnal variation), acute stress, sleep disruption, estrogen status (oral contraceptives, pregnancy increase binding protein), chronic illness, and medications.

The concentration of vitamin D2 circulating in the blood, which reflects recent dietary intake of D2-fortified foods or ergocalciferol supplementation.

Elevated levels indicate excessive D2 supplementation and may contribute to toxicity if total vitamin D is significantly raised. In unsupplemented individuals, undetectable D2 is normal and expected; in patients on D2 therapy, low levels may indicate malabsorption. Vitamin D2 status can be influenced by malabsorption disorders, liver disease, and medications such as anticonvulsants.

The serum concentration of 25-hydroxyvitamin D3, reflecting the combination of sun exposure, dietary intake from animal sources (fatty fish, egg yolks, liver), and D3 supplementation.

Elevated levels indicate excessive supplementation or sun exposure and may contribute to hypercalcemia, hypercalciuria, and soft tissue calcification if total vitamin D exceeds safe thresholds. Low levels suggest inadequate sun exposure, poor dietary intake, malabsorption, liver dysfunction, or increased catabolism from certain medications. Vitamin D3 status can be influenced by geographic latitude, skin pigmentation, age, obesity, kidney disease, liver disease, and medications such as anticonvulsants and glucocorticoids.

The combined serum concentration of both D2 and D3 metabolites, reflecting total vitamin D obtained from sun exposure, diet, and supplementation.

Elevated levels indicate excessive supplementation and may cause hypercalcemia, hypercalciuria, nausea, weakness, and kidney damage. Low levels indicate deficiency, which can lead to secondary hyperparathyroidism, reduced bone mineral density, osteomalacia, muscle weakness, and increased fracture risk. Total vitamin D status can be influenced by sun exposure, geographic latitude, skin pigmentation, age, obesity, malabsorption syndromes, liver disease, kidney disease, and medications such as anticonvulsants and glucocorticoids.

Elevated levels may indicate iron overload (hemochromatosis), liver disease, chronic inflammation, infection, obesity, alcohol use, or malignancy.

Elevated levels may indicate iron overload (hemochromatosis), liver disease, chronic inflammation, infection, obesity, alcohol use, or malignancy (cancer or other diseases). Low levels are highly specific for iron deficiency and indicate depleted iron stores, often preceding anemia. Ferritin status can be influenced by inflammation, infection, liver disease, obesity, alcohol consumption, malignancy, pregnancy, and recent blood transfusions—all of which can falsely elevate ferritin even when iron stores are actually low.

Red blood cell membrane arachidonic acid concentration reflects long-term omega-6 intake and the availability of substrate for inflammatory mediator synthesis.

Elevated arachidonic acid may indicate pro-inflammatory status, high dietary omega-6 intake, or imbalance in the omega-6 to omega-3 ratio. Low arachidonic acid is uncommon given typical Western dietary patterns; very low levels may indicate essential fatty acid deficiency. Arachidonic acid status can be influenced by dietary intake (meat, eggs, poultry), linoleic acid conversion, genetic polymorphisms (FADS genes), and omega-3 intake (which competes for membrane incorporation).

This ratio reflects the relative availability of substrates for pro-inflammatory versus anti-inflammatory eicosanoid synthesis, with lower ratios indicating a less inflammatory metabolic environment.

Elevated AA/EPA ratio indicates omega-6 predominance and a pro-inflammatory fatty acid profile, associated with increased cardiovascular and inflammatory disease risk. Lower ratios indicate favorable omega-3 to omega-6 balance with greater anti-inflammatory capacity. AA/EPA ratio can be influenced by fatty fish consumption, fish oil supplementation, dietary omega-6 intake (vegetable oils, processed foods), and genetic factors affecting fatty acid metabolism.

Red blood cell membrane DHA concentration, expressed as a percentage of total fatty acids, reflects tissue DHA status and long-term dietary intake or supplementation over the preceding 2–3 months.

Higher DHA levels are associated with cognitive benefits, reduced inflammation, and cardiovascular protection. Low DHA levels may indicate insufficient omega-3 intake and are associated with cognitive decline risk, depression, and cardiovascular disease. DHA status can be influenced by fatty fish consumption, algal or fish oil supplementation, genetic polymorphisms (FADS genes), and limited conversion from alpha-linolenic acid (ALA).

Red blood cell membrane DPA concentration, expressed as a percentage of total fatty acids, reflects omega-3 intake and the body's metabolic handling of marine-derived omega-3 fatty acids.

Higher DPA levels may provide additional anti-inflammatory and cardiovascular benefits beyond EPA and DHA alone. Low DPA levels typically parallel low EPA and DHA status. DPA status can be influenced by fatty fish consumption, supplementation, and genetic factors affecting elongase enzyme activity.

Red blood cell membrane EPA concentration, expressed as a percentage of total fatty acids, reflects long-term dietary omega-3 intake and tissue incorporation over the preceding 2–3 months.

Higher EPA levels are associated with reduced inflammation, lower triglycerides, and cardiovascular protection. Low EPA levels may indicate insufficient omega-3 intake and are associated with elevated inflammatory markers and cardiovascular risk. EPA status can be influenced by fatty fish consumption, fish oil supplementation, genetic polymorphisms affecting fatty acid metabolism (FADS genes), and competition with omega-6 fatty acids for incorporation into cell membranes.

This combined measurement reflects tissue-level omega-3 fatty acid incorporation over the preceding 2–3 months, providing a more stable indicator of omega-3 status than plasma measurements which fluctuate with recent dietary intake.

Higher Omega-3 Index levels (8–12%) are associated with cardioprotection, reduced sudden cardiac death risk, improved cognitive outcomes, and anti-inflammatory benefits. Low Omega-3 Index (<4%) is associated with elevated cardiovascular risk; 4–8% represents intermediate risk. Omega-3 Index can be influenced by fatty fish consumption frequency, fish oil or algal oil supplementation, genetic polymorphisms (FADS genes), and baseline omega-6 intake.

Red blood cell membrane linoleic acid concentration reflects long-term dietary omega-6 intake and serves as the precursor for arachidonic acid synthesis.

High linoleic acid levels may indicate substantial vegetable oil consumption and potentially unfavorable omega-6 to omega-3 balance. Very low levels may indicate essential fatty acid deficiency, though this is rare in Western populations. Linoleic acid status can be influenced by vegetable oil consumption, nut and seed intake, processed food consumption, and genetic factors affecting elongase and desaturase enzymes.

This measurement reflects the complete omega-3 fatty acid content of cell membranes, though EPA and DHA (marine-derived) are the most biologically active forms.

Higher total omega-3 status is associated with anti-inflammatory benefits and cardiovascular protection. Low total omega-3 indicates insufficient intake of both plant-based (ALA) and marine-derived (EPA, DHA) omega-3 sources. Total omega-3 can be influenced by dietary sources (fatty fish, flaxseed, walnuts, chia seeds), supplementation, and genetic conversion efficiency for ALA to EPA/DHA.

This measurement reflects the complete omega-6 fatty acid content of cell membranes, predominantly influenced by vegetable oil and processed food consumption in Western diets.

High total omega-6 may indicate excessive vegetable oil consumption and unfavorable balance relative to omega-3 intake. Low omega-6 is uncommon in Western populations given ubiquitous presence in processed foods. Total omega-6 can be influenced by vegetable oil intake (corn, soybean, sunflower), processed food consumption, and nut and seed intake.

This ratio reflects the competitive relationship between pro-inflammatory omega-6 and anti-inflammatory omega-3 fatty acids for membrane incorporation and enzymatic conversion to signaling molecules.

Elevated ratios (typical Western diet: 15:1 to 25:1) are associated with increased inflammatory disease risk, cardiovascular disease, and chronic conditions. Lower ratios (4:1 or less) are associated with reduced cardiovascular and inflammatory disease risk. This ratio can be influenced by vegetable oil consumption, fatty fish intake, supplementation, and processed food consumption. Clinical focus should emphasize raising omega-3 intake rather than severely restricting omega-6.

Serum B12 concentration reflects circulating cobalamin bound to transcobalamin and haptocorrin transport proteins, though serum levels may not fully reflect tissue status in all cases.

Elevated levels may indicate recent supplementation, liver disease (hepatocellular release), renal failure (impaired clearance), diabetes, or rarely certain hematologic malignancies (chronic myelogenous leukemia). Low levels may indicate pernicious anemia (anti-intrinsic factor antibodies), dietary insufficiency (vegans, vegetarians), malabsorption syndromes (celiac, Crohn's, gastric bypass), atrophic gastritis, long-term use of proton pump inhibitors or metformin, or H. pylori infection. B12 status can be influenced by dietary intake, intrinsic factor availability, gastric acid production, intestinal absorption capacity, age (decreased absorption with aging), and medications (Proton Pump Inhibitors, H2 blockers, metformin).

Serum folate concentration reflects recent dietary intake and circulating folate status, though red blood cell folate provides a more stable indicator of tissue stores over time.

Elevated serum folate typically reflects recent supplementation or folate-rich meal consumption; very high levels may mask underlying B12 deficiency while partially correcting hematological abnormalities. Low levels may indicate dietary insufficiency, malabsorption, alcoholism, increased requirements (pregnancy, hemolytic anemia), or certain medications (methotrexate, phenytoin, metformin). Folate status can be influenced by dietary intake (leafy greens, legumes, fortified grains), recent meals (serum levels fluctuate with intake), alcohol consumption, pregnancy, and medications affecting folate metabolism.

This percentage reflects the balance between iron supply and transport capacity, providing context for interpreting serum iron and TIBC values in diagnosing iron disorders.

Elevated saturation (>45–50%) may indicate hemochromatosis, iron overload, hemolytic anemia, sideroblastic anemia, or acute hepatitis; saturation >70% in females or >80% in males suggests parenchymal iron loading. (<20% in males, <15% in females) combined with low serum iron and high TIBC indicates iron deficiency anemia. Iron saturation can be influenced by recent dietary intake, timing of blood draw, inflammation, and the conditions affecting both serum iron and transferrin levels.

TIBC indirectly reflects transferrin concentration and indicates the reserve capacity for iron transport, with the relationship between TIBC and serum iron used to calculate percent saturation.

Elevated TIBC may indicate iron deficiency (compensatory increase in transferrin production), oral contraceptive use, or pregnancy. Low TIBC may indicate anemia of chronic disease, malnutrition, protein-losing conditions (nephrotic syndrome), cirrhosis, or hemochromatosis. TIBC can be influenced by nutritional status, inflammatory conditions (acute phase reactant response), liver function, and estrogen status.

Serum iron concentration reflects the amount of iron immediately available for physiological use, though levels fluctuate significantly with recent dietary intake and exhibit diurnal variation.

Elevated levels may indicate hemochromatosis, iron overload from transfusions, hemolytic anemia, sideroblastic anemia, acute hepatitis, or excessive iron supplementation. Low levels may indicate iron deficiency anemia, chronic blood loss, inadequate dietary intake, malabsorption, chronic disease (anemia of chronic disease with impaired iron release from stores), or recovery from pernicious anemia treatment. Serum iron can be influenced by recent dietary intake, time of day (diurnal variation), acute infection or inflammation (decreased), recent blood transfusion, and certain medications.

The concentration of thyroid-stimulating hormone in blood, which reflects how hard the pituitary gland is working to stimulate the thyroid. It serves as the primary screening test for thyroid disorders.

Elevated levels may indicate primary hypothyroidism (most common), Hashimoto's thyroiditis, subclinical hypothyroidism, iodine deficiency, recovery phase from severe illness, or rarely TSH-secreting pituitary adenoma. Low levels may indicate pimary hyperthyroidism (most common), Graves' disease, toxic nodular goiter, thyroiditis (thyrotoxic phase), overmedication with thyroid hormone, central hypothyroidism (pituitary/hypothalamic dysfunction), nonthyroidal illness, or first trimester pregnancy. TSH levels fluctuate daily (highest in the early morning) and can be suppressed by acute stress, starvation, or biotin supplements, potentially masking true thyroid status.

The concentration of unbound, biologically active thyroxine. When TSH is abnormal, Free T4 determines whether actual thyroid hormone production is affected and distinguishes primary thyroid disorders from pituitary/hypothalamic problems. *If TSH is abnormal, Free T4 is automatically performed on the same sample.

Elevated levels may indicate hyperthyroidism, Graves' disease, toxic nodular goiter, thyroiditis (inflammatory phase), excessive thyroid medication, iodine-containing contrast agents or amiodarone exposure. Low levels may indicate primary hypothyroidism (with elevated TSH), central hypothyroidism (with low/normal TSH), severe nonthyroidal illness, inadequate thyroid hormone replacement, or medications increasing thyroid hormone metabolism. Biotin can cause falsely elevated readings. Heparin, amiodarone, propranolol, and contrast agents may increase Free T4. Phenytoin, carbamazepine, and rifampin may decrease it.

The concentration of unbound, biologically active thyroxine. When TSH is abnormal, Free T4 determines whether actual thyroid hormone production is affected and distinguishes primary thyroid disorders from pituitary/hypothalamic problems.

Elevated levels may indicate hyperthyroidism, Graves' disease, toxic nodular goiter, thyroiditis (inflammatory phase), excessive thyroid medication, iodine-containing contrast agents or amiodarone exposure. Low levels may indicate primary hypothyroidism (with elevated TSH), central hypothyroidism (with low/normal TSH), severe nonthyroidal illness, inadequate thyroid hormone replacement, or medications increasing thyroid hormone metabolism. Biotin can cause falsely elevated readings. Heparin, amiodarone, propranolol, and contrast agents may increase Free T4. Phenytoin, carbamazepine, and rifampin may decrease it.

The concentration of T3 not bound to thyroid-binding proteins, representing the bioavailable hormone directly accessible to tissues.

Elevated levels indicate hyperthyroidism (Graves' disease) or over-medication with thyroid hormone (especially Cytomel/Liothyronine). Low levels indicate hypothyroidism or "conversion issues," where the body has enough T4 but isn't converting it efficiently into active T3 (often due to stress, liver issues, or nutrient deficiencies like selenium). Free T3 status can be influenced by acute illness, fasting, medications (amiodarone, beta-blockers, corticosteroids), pregnancy, and protein-binding abnormalities.

The concentration of antibodies targeting thyroid peroxidase, reflecting autoimmune activity against the thyroid gland.

Elevated levels indicate Hashimoto's thyroiditis, Graves’ disease, postpartum thyroiditis, increased risk of thyroid dysfunction progression, associated with other autoimmune conditions. Low or undetectable levels are normal and indicate no autoimmune attack is present. TPO antibody status can be influenced by iodine intake, pregnancy, age, sex (more prevalent in women), and coexisting autoimmune diseases such as type 1 diabetes or rheumatoid arthritis.

The concentration of antibodies targeting thyroglobulin protein, reflecting autoimmune thyroid activity.

Elevated levels are found in Hashimoto’s Thyroiditis and Graves’ disease; they are also used to monitor thyroid cancer patients. Low or undetectable levels are normal. Thyroglobulin antibody status can be influenced by iodine intake, pregnancy, coexisting autoimmune conditions, and thyroid surgery or radioiodine ablation (levels typically decline post-treatment if cancer is adequately treated).