Metformin (Generic)
Metformin is an oral medication used to help manage blood sugar. It works by reducing glucose production in the liver, decreasing intestinal absorption of glucose, and improving the body’s response to insulin.
*Prescription required. Results may vary. For additional information, see product information.
Metformin is taken orally, typically with food to reduce the chance of stomach discomfort. It is available in immediate-release and extended-release tablets. Your physician will determine your starting dose and schedule based on your lab results and clinical evaluation, and may increase the dose gradually over several weeks to minimize side effects.
Important Safety Information — Metformin
What is metformin?
Metformin is a prescription medicine containing metformin hydrochloride. It is used with diet and exercise to help control high blood sugar in patients with type 2 diabetes.
Metformin immediate-release tablets may be used in adults and pediatric patients 10 years of age and older. Metformin extended-release tablets are used in adults. Metformin is not for people with type 1 diabetes or diabetic ketoacidosis.
This page does not include all possible information about metformin. Always follow your prescription label and the instructions provided by your healthcare provider or pharmacist.
Boxed Warning: Lactic Acidosis
Metformin can cause a rare but serious condition called lactic acidosis, which is a buildup of lactic acid in the blood. Lactic acidosis is a medical emergency and can be fatal.
Stop taking metformin and seek medical care right away if you feel very weak or tired, have unusual muscle pain, have trouble breathing, feel unusually sleepy, have unexplained stomach or intestinal symptoms such as nausea, vomiting, diarrhea, or abdominal pain, feel cold especially in your arms or legs, feel dizzy or lightheaded, or have a slow or irregular heartbeat.
The risk of lactic acidosis may be higher in patients with kidney problems, liver problems, congestive heart failure, dehydration, excessive alcohol intake, serious infection, heart attack, stroke, surgery, radiology procedures involving injectable contrast dye, use of certain medications, or older age.
Who should not take metformin?
Do not take metformin if you have severe kidney impairment, including an estimated glomerular filtration rate below 30 mL/min/1.73 m².
Do not take metformin if you are allergic to metformin hydrochloride or any ingredient in your medication.
Do not take metformin if you have acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma.
Kidney Function
Your kidney function should be checked before starting metformin and periodically during treatment.
Metformin should not be started in patients with an eGFR between 30 and 45 mL/min/1.73 m². If your eGFR falls below 45 mL/min/1.73 m² while taking metformin, your healthcare provider should reassess whether treatment should continue. Metformin should be stopped if eGFR falls below 30 mL/min/1.73 m².
Radiology Procedures, Surgery, and Dehydration
Metformin may need to be stopped before or at the time of certain radiology procedures involving iodinated contrast dye, especially in patients with reduced kidney function, liver disease, alcoholism, heart failure, or intra-arterial contrast exposure. Kidney function should be reassessed before metformin is restarted.
Metformin may also need to be temporarily stopped during surgery, procedures, serious illness, dehydration, restricted food or fluid intake, or other situations that may increase the risk of kidney problems or lactic acidosis.
Liver Impairment
Metformin is not recommended in patients with liver impairment. Liver impairment may increase the risk of metformin-associated lactic acidosis.
Alcohol
Avoid excessive alcohol intake while taking metformin. Alcohol can increase the effect of metformin on lactate metabolism and may increase the risk of lactic acidosis.
Vitamin B12 Deficiency
Metformin may lower vitamin B12 levels. Your healthcare provider may monitor blood counts each year and vitamin B12 levels every 2 to 3 years, especially if you have anemia, nerve symptoms, low vitamin B12 intake, or risk factors for reduced vitamin B12 absorption.
Low Blood Sugar
Metformin usually does not cause low blood sugar by itself. Low blood sugar may occur if metformin is used with insulin, sulfonylureas, or other medications that lower blood sugar, or if you do not eat enough or drink alcohol.
Symptoms of low blood sugar may include sweating, shakiness, hunger, dizziness, headache, confusion, irritability, weakness, or a fast heartbeat. Follow your healthcare provider’s instructions for treating low blood sugar.
Possible Side Effects
Common side effects of metformin include diarrhea, nausea, vomiting, gas, weakness, indigestion, abdominal discomfort, headache, and upset stomach. Taking metformin with meals may help reduce stomach-related side effects.
Other reported side effects include abnormal stools, muscle pain, lightheadedness, shortness of breath, rash, increased sweating, taste changes, chest discomfort, chills, flu-like symptoms, flushing, palpitations, constipation, abdominal distention, heartburn, dizziness, upper respiratory infection, and metallic taste.
Diarrhea, nausea, and upset stomach often improve after the body adjusts to metformin. Tell your healthcare provider if side effects are severe, last more than a few weeks, return after going away, or begin later in treatment.
Liver injury, including cholestatic, hepatocellular, and mixed hepatocellular liver injury, has been reported after approval of metformin.
Drug Interactions
Tell your healthcare provider about all medications, vitamins, and supplements you take. Some medicines may affect metformin, and metformin may affect other medicines.
Carbonic anhydrase inhibitors may increase the risk of lactic acidosis when used with metformin. Examples include topiramate, zonisamide, acetazolamide, and dichlorphenamide.
Some drugs may reduce metformin clearance and increase metformin exposure. Examples include ranolazine, vandetanib, dolutegravir, and cimetidine.
Insulin and insulin secretagogues such as sulfonylureas may increase the risk of low blood sugar when used with metformin. A dose adjustment of insulin or the insulin secretagogue may be needed.
Some drugs can affect blood sugar control, including thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blockers, and isoniazid.
Pregnancy
Limited data with metformin in pregnant women are not sufficient to determine a drug-associated risk for major birth defects or miscarriage. Poorly controlled diabetes during pregnancy can create risks for both the mother and fetus. If you are pregnant or planning to become pregnant, talk with your healthcare provider about the best way to control blood sugar during pregnancy.
Breastfeeding
Metformin is present in human milk. There is not enough information to determine the effects of metformin on the breastfed infant or on milk production. Talk with your healthcare provider about the benefits and risks of breastfeeding while taking metformin.
Females of Reproductive Potential
Metformin may result in ovulation in some premenopausal women who do not ovulate regularly, which may increase the chance of unintended pregnancy.
Pediatric Use
Metformin immediate-release tablets have been studied in pediatric patients 10 to 16 years of age with type 2 diabetes. Safety and effectiveness have not been established in pediatric patients younger than 10 years of age.
Safety and effectiveness of metformin extended-release tablets have not been established in pediatric patients.
Geriatric Use
Older adults may have a higher risk of lactic acidosis because they are more likely to have reduced kidney, liver, or heart function. Kidney function should be assessed more frequently in older patients taking metformin.
How to Take Metformin
Take metformin exactly as prescribed. Metformin should be taken with meals to help reduce stomach-related side effects.
If you take metformin extended-release tablets, swallow the tablet whole. Do not crush, cut, or chew extended-release tablets.
You may occasionally notice a soft mass in your stool that looks like an extended-release tablet. This can occur with extended-release tablets and does not necessarily mean the medication failed to work.
Missed Dose
If you miss a dose, take your next dose as prescribed unless your healthcare provider tells you differently.
Do not take an extra dose the next day to make up for a missed dose.
Overdose
Metformin overdose can occur and has been associated with lactic acidosis. If you take too much metformin, seek medical attention immediately or contact Poison Control at 1-800-222-1222.
Storage
Store metformin at 20°C to 25°C / 68°F to 77°F. Keep medication in a secure place and out of reach of children.
Medication Disposal
Do not flush unused medication down the toilet or pour it into a sink or drain unless specifically instructed.
Follow local disposal guidance or ask your pharmacist how to safely dispose of unused medication.
Reporting Side Effects
Tell your healthcare provider if you experience side effects or symptoms that concern you.
You may report suspected adverse reactions to the FDA through MedWatch at 1-800-FDA-1088 or www.fda.gov/medwatch.
Telemedicine Disclosure
This prescription may be issued through telemedicine after review by a licensed healthcare provider. If you experience concerning symptoms, contact your healthcare provider or seek emergency medical care.
Withholding or providing inaccurate information about your symptoms, medical history, medications, allergies, prior reactions, kidney function, liver function, pregnancy status, breastfeeding status, alcohol use, or other relevant health information may result in serious harm.
Disclaimer
This information is not comprehensive and does not include all possible risks, side effects, interactions, warnings, or precautions associated with metformin. This page does not provide medical advice, diagnosis, or treatment.
For questions about your medication, prescription, dosing, side effects, or treatment plan, contact your healthcare provider or pharmacist.
For more information, see the full prescribing information for metformin.
You are encouraged to report negative side effects of prescription products:
- Contact FDA MedWatch at 1-800-FDA-1088 or visit www.fda.gov/medwatch
All medications require a consultation with a licensed physician who will determine if treatment is appropriate based on your labs and medical history.
Important Safety Information
Important Safety Information — Metformin
What is metformin?
Metformin is a prescription medicine containing metformin hydrochloride. It is used with diet and exercise to help control high blood sugar in patients with type 2 diabetes.
Metformin immediate-release tablets may be used in adults and pediatric patients 10 years of age and older. Metformin extended-release tablets are used in adults. Metformin is not for people with type 1 diabetes or diabetic ketoacidosis.
This page does not include all possible information about metformin. Always follow your prescription label and the instructions provided by your healthcare provider or pharmacist.
Boxed Warning: Lactic Acidosis
Metformin can cause a rare but serious condition called lactic acidosis, which is a buildup of lactic acid in the blood. Lactic acidosis is a medical emergency and can be fatal.
Stop taking metformin and seek medical care right away if you feel very weak or tired, have unusual muscle pain, have trouble breathing, feel unusually sleepy, have unexplained stomach or intestinal symptoms such as nausea, vomiting, diarrhea, or abdominal pain, feel cold especially in your arms or legs, feel dizzy or lightheaded, or have a slow or irregular heartbeat.
The risk of lactic acidosis may be higher in patients with kidney problems, liver problems, congestive heart failure, dehydration, excessive alcohol intake, serious infection, heart attack, stroke, surgery, radiology procedures involving injectable contrast dye, use of certain medications, or older age.
Who should not take metformin?
Do not take metformin if you have severe kidney impairment, including an estimated glomerular filtration rate below 30 mL/min/1.73 m².
Do not take metformin if you are allergic to metformin hydrochloride or any ingredient in your medication.
Do not take metformin if you have acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma.
Kidney Function
Your kidney function should be checked before starting metformin and periodically during treatment.
Metformin should not be started in patients with an eGFR between 30 and 45 mL/min/1.73 m². If your eGFR falls below 45 mL/min/1.73 m² while taking metformin, your healthcare provider should reassess whether treatment should continue. Metformin should be stopped if eGFR falls below 30 mL/min/1.73 m².
Radiology Procedures, Surgery, and Dehydration
Metformin may need to be stopped before or at the time of certain radiology procedures involving iodinated contrast dye, especially in patients with reduced kidney function, liver disease, alcoholism, heart failure, or intra-arterial contrast exposure. Kidney function should be reassessed before metformin is restarted.
Metformin may also need to be temporarily stopped during surgery, procedures, serious illness, dehydration, restricted food or fluid intake, or other situations that may increase the risk of kidney problems or lactic acidosis.
Liver Impairment
Metformin is not recommended in patients with liver impairment. Liver impairment may increase the risk of metformin-associated lactic acidosis.
Alcohol
Avoid excessive alcohol intake while taking metformin. Alcohol can increase the effect of metformin on lactate metabolism and may increase the risk of lactic acidosis.
Vitamin B12 Deficiency
Metformin may lower vitamin B12 levels. Your healthcare provider may monitor blood counts each year and vitamin B12 levels every 2 to 3 years, especially if you have anemia, nerve symptoms, low vitamin B12 intake, or risk factors for reduced vitamin B12 absorption.
Low Blood Sugar
Metformin usually does not cause low blood sugar by itself. Low blood sugar may occur if metformin is used with insulin, sulfonylureas, or other medications that lower blood sugar, or if you do not eat enough or drink alcohol.
Symptoms of low blood sugar may include sweating, shakiness, hunger, dizziness, headache, confusion, irritability, weakness, or a fast heartbeat. Follow your healthcare provider’s instructions for treating low blood sugar.
Possible Side Effects
Common side effects of metformin include diarrhea, nausea, vomiting, gas, weakness, indigestion, abdominal discomfort, headache, and upset stomach. Taking metformin with meals may help reduce stomach-related side effects.
Other reported side effects include abnormal stools, muscle pain, lightheadedness, shortness of breath, rash, increased sweating, taste changes, chest discomfort, chills, flu-like symptoms, flushing, palpitations, constipation, abdominal distention, heartburn, dizziness, upper respiratory infection, and metallic taste.
Diarrhea, nausea, and upset stomach often improve after the body adjusts to metformin. Tell your healthcare provider if side effects are severe, last more than a few weeks, return after going away, or begin later in treatment.
Liver injury, including cholestatic, hepatocellular, and mixed hepatocellular liver injury, has been reported after approval of metformin.
Drug Interactions
Tell your healthcare provider about all medications, vitamins, and supplements you take. Some medicines may affect metformin, and metformin may affect other medicines.
Carbonic anhydrase inhibitors may increase the risk of lactic acidosis when used with metformin. Examples include topiramate, zonisamide, acetazolamide, and dichlorphenamide.
Some drugs may reduce metformin clearance and increase metformin exposure. Examples include ranolazine, vandetanib, dolutegravir, and cimetidine.
Insulin and insulin secretagogues such as sulfonylureas may increase the risk of low blood sugar when used with metformin. A dose adjustment of insulin or the insulin secretagogue may be needed.
Some drugs can affect blood sugar control, including thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blockers, and isoniazid.
Pregnancy
Limited data with metformin in pregnant women are not sufficient to determine a drug-associated risk for major birth defects or miscarriage. Poorly controlled diabetes during pregnancy can create risks for both the mother and fetus. If you are pregnant or planning to become pregnant, talk with your healthcare provider about the best way to control blood sugar during pregnancy.
Breastfeeding
Metformin is present in human milk. There is not enough information to determine the effects of metformin on the breastfed infant or on milk production. Talk with your healthcare provider about the benefits and risks of breastfeeding while taking metformin.
Females of Reproductive Potential
Metformin may result in ovulation in some premenopausal women who do not ovulate regularly, which may increase the chance of unintended pregnancy.
Pediatric Use
Metformin immediate-release tablets have been studied in pediatric patients 10 to 16 years of age with type 2 diabetes. Safety and effectiveness have not been established in pediatric patients younger than 10 years of age.
Safety and effectiveness of metformin extended-release tablets have not been established in pediatric patients.
Geriatric Use
Older adults may have a higher risk of lactic acidosis because they are more likely to have reduced kidney, liver, or heart function. Kidney function should be assessed more frequently in older patients taking metformin.
How to Take Metformin
Take metformin exactly as prescribed. Metformin should be taken with meals to help reduce stomach-related side effects.
If you take metformin extended-release tablets, swallow the tablet whole. Do not crush, cut, or chew extended-release tablets.
You may occasionally notice a soft mass in your stool that looks like an extended-release tablet. This can occur with extended-release tablets and does not necessarily mean the medication failed to work.
Missed Dose
If you miss a dose, take your next dose as prescribed unless your healthcare provider tells you differently.
Do not take an extra dose the next day to make up for a missed dose.
Overdose
Metformin overdose can occur and has been associated with lactic acidosis. If you take too much metformin, seek medical attention immediately or contact Poison Control at 1-800-222-1222.
Storage
Store metformin at 20°C to 25°C / 68°F to 77°F. Keep medication in a secure place and out of reach of children.
Medication Disposal
Do not flush unused medication down the toilet or pour it into a sink or drain unless specifically instructed.
Follow local disposal guidance or ask your pharmacist how to safely dispose of unused medication.
Reporting Side Effects
Tell your healthcare provider if you experience side effects or symptoms that concern you.
You may report suspected adverse reactions to the FDA through MedWatch at 1-800-FDA-1088 or www.fda.gov/medwatch.
Telemedicine Disclosure
This prescription may be issued through telemedicine after review by a licensed healthcare provider. If you experience concerning symptoms, contact your healthcare provider or seek emergency medical care.
Withholding or providing inaccurate information about your symptoms, medical history, medications, allergies, prior reactions, kidney function, liver function, pregnancy status, breastfeeding status, alcohol use, or other relevant health information may result in serious harm.
Disclaimer
This information is not comprehensive and does not include all possible risks, side effects, interactions, warnings, or precautions associated with metformin. This page does not provide medical advice, diagnosis, or treatment.
For questions about your medication, prescription, dosing, side effects, or treatment plan, contact your healthcare provider or pharmacist.
For more information, see the full prescribing information for metformin.
Why Metformin with ATHS?
Because effective treatment should be accessible from home and backed by real clinical oversight.
- No mandatory subscription plans
- Dispensed by a licensed U.S. pharmacy
- HSA / FSA eligible
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