Overview

Active ingredient: Metformin

Main use: Type 2 diabetes mellitus management

Typical strengths available: 250 mg, 500 mg, 850 mg, 1000 mg

Glucophage is an oral antidiabetic medication whose active ingredient, metformin, is in the biguanide class. It helps lower blood glucose primarily by decreasing glucose production in the liver, improving insulin sensitivity in muscles and other tissues, and modestly reducing glucose absorption from the gut. It does not treat type 1 diabetes and is not effective if there is no insulin activity in the body.

  • Often weight-neutral and may help prevent modest weight gain compared with some other diabetes medicines.
  • Low risk of causing hypoglycemia when used alone, because it does not directly increase insulin secretion.
  • Used as first-line therapy for many adults with type 2 diabetes, including those who did not respond well to lifestyle changes alone.

For quick jumps: see Dosage and Direction, Precautions, or Alternatives.

Dosage and Direction

Use Glucophage only if it has been prescribed to you. Follow your prescriber's instructions and do not exceed the recommended amount. Taking the medicine with food can improve stomach tolerability unless directed otherwise by your clinician.

  • Usual starting regimens include 500 mg twice daily or 850 mg once daily with meals.
  • Based on blood glucose targets and tolerability, the dose may be raised gradually to a typical maximum of 2550 mg per day in 2 to 3 divided doses.
  • Extended-release versions (if prescribed) are usually taken once daily with the evening meal and have different maximum doses; check the specific product label.

If you have questions on changing your dose, speak with your healthcare provider. For what to do if a dose is missed or if too much is taken, see Missed Dose and Overdose.

Important Warnings and Precautions

Metformin can, in rare cases, lead to a serious condition known as lactic acidosis. Seek emergency care if you notice symptoms such as unusual weakness, excessive sleepiness, slow or irregular heartbeat, feeling very cold, muscle pain, stomach pain, shortness of breath, dizziness, or fainting.

  • Avoid or limit alcohol, which increases the risk of lactic acidosis and low blood sugar.
  • Hold metformin before certain imaging procedures with iodinated contrast and major surgery. Your clinician will tell you when to stop and when to restart after kidney function is reassessed.
  • Be alert for signs of low blood sugar, especially if you use metformin together with insulin or other glucose-lowering drugs: hunger, sweating, trembling, fast heartbeat, headache, drowsiness, confusion, irritability, or seizures. Keep a rapid source of sugar on hand.
  • Kidney function matters. People with severe renal impairment must not use metformin. Your prescriber will monitor eGFR and adjust or stop therapy if needed.

For details on people who should avoid this medicine entirely, jump to Contraindications.

Contraindications - Do Not Use If

  • You have severe kidney disease or a history of lactic acidosis.
  • You are significantly dehydrated, have acute or chronic metabolic acidosis, or are in a hyperglycemic crisis such as ketoacidosis or hyperosmolar coma.
  • You have severe liver disease, unstable heart failure, recent acute myocardial infarction, or significant respiratory failure.
  • You are undergoing major surgery or an imaging study using iodinated contrast without clinician guidance on when to stop and restart.
  • Alcoholism or very low calorie diets (generally under 1000 kcal per day) increase risk and are not compatible with therapy.
  • Pregnancy or breastfeeding, unless your clinician specifically advises otherwise.

Caution may be required in older adults over 60 who perform strenuous physical work, as the risk of lactic acidosis could be higher in the setting of dehydration or acute illness.

Possible Side Effects

Many effects are gastrointestinal and often improve after dose adjustment or when taken with food.

  • Common: nausea, vomiting, diarrhea, gas, bloating, reduced appetite, or a metallic taste.
  • Fluid retention or rapid weight changes are not typical with metformin; report such symptoms promptly.
  • Allergic reactions can occur: hives, rash, swelling. Seek medical attention for signs of anaphylaxis.
  • Emergency care is needed for symptoms suggestive of lactic acidosis: worsening drowsiness, slow heartbeat, cold sensation, trouble breathing, abdominal pain, muscle aches, dizziness, or fainting.

Report persistent or severe adverse reactions to your healthcare professional and see Precautions for risk factors.

Drug and Substance Interactions

Some medicines can increase or decrease the glucose-lowering effect of metformin or raise side effect risks.

  • Do not combine with excessive alcohol; serious adverse effects can occur.
  • Cimetidine (Tagamet) can increase metformin levels; monitoring or alternatives may be needed.
  • Metformin effects may be increased by insulin, sulfonylureas, acarbose, MAO inhibitors, cyclophosphamide, salicylates, and some antibiotics like oxytetracycline.
  • Decreased metformin effect has been reported with certain thyroid hormones, estrogen or progestin contraceptives, epinephrine, glucagon, thiazide diuretics, and high-dose niacin.
  • Furosemide metabolism may be affected when used with metformin; clinical monitoring is recommended.

Always provide your clinician and pharmacist with a complete list of prescriptions, OTC drugs, and supplements.

Missed Dose and Overdose

If you miss a dose: Take it when you remember unless it is close to the next scheduled dose. If so, skip the missed dose. Do not double up.

Overdose warning: Symptoms may include profound low blood sugar if taken with other antidiabetic agents, or signs of lactic acidosis. Other symptoms can include confusion, irritability, drowsiness, headache, weakness, tremors, sweating, fast heartbeat, or seizures. Call your clinician or emergency services immediately. Keep a rapid sugar source available if you are on additional glucose-lowering medications.

Return to top or see Dosage.

Storage

  • Store at 20-25 C (68-77 F) and protect from moisture, heat, and direct light.
  • Do not store in the bathroom. Keep out of reach of children and pets.
  • Check the bottle for expiration dates and do not use past expiry.

Alternatives and Similar Medicines

If Glucophage is not suitable or additional control is needed, clinicians in the USA may consider:

  • Metformin extended-release brands and generics: Glucophage XR, Fortamet, Glumetza. Similar efficacy with improved GI tolerability for some patients.
  • Sulfonylureas: glipizide, glyburide, glimepiride. Lower cost but higher hypoglycemia risk and potential for weight gain.
  • DPP-4 inhibitors: sitagliptin, linagliptin, alogliptin, saxagliptin. Weight neutral and low hypoglycemia risk; moderate A1C lowering.
  • SGLT2 inhibitors: empagliflozin, canagliflozin, dapagliflozin, ertugliflozin. Cardio-renal benefits in appropriate patients; risk of genital infections and dehydration.
  • GLP-1 receptor agonists: semaglutide, liraglutide, dulaglutide, tirzepatide (dual GIP/GLP-1). Strong A1C and weight effects; injectable or oral options, typically higher cost.
  • Thiazolidinediones: pioglitazone. Useful for insulin resistance; may cause weight gain or edema.
  • Insulin therapies: basal and bolus formulations. Essential for type 1 diabetes and sometimes used in type 2; highest hypoglycemia risk if misused.

Choice depends on clinical goals, kidney function, cardiovascular and kidney disease history, weight considerations, cost, and patient preference. Discuss options with your prescriber. Jump to Prices for ballpark costs.

Typical Prices in the USA (USD)

Prices vary by pharmacy, insurance, discount cards, and formulation. The following are rough cash price ranges for 30 days unless noted otherwise:

  • Metformin immediate-release generic (500 mg or 850 mg, 60-120 tablets): about $4 to $15 at discount retailers; commonly under $20.
  • Metformin ER generic (500 mg or 750 mg, 30-90 tablets): about $10 to $40 depending on dose and quantity.
  • Brand ER formulations (Glumetza, Fortamet): can range widely, commonly $200 to $600+ per month without insurance.
  • Alternative classes for comparison: DPP-4 inhibitors often $500 to $600 per month; SGLT2 inhibitors around $500 to $650; GLP-1 RAs $900 to $1200+; sulfonylureas typically $5 to $20; pioglitazone about $10 to $25; human insulin vials roughly $25 to $150 depending on brand and program.

Check local pharmacies, manufacturer coupons, discount programs, and insurance formularies for exact pricing.

Disclaimer

The information on this page is educational and general. It does not include every possible precaution, interaction, or instruction. Do not use it for self-diagnosis or to start, stop, or change medication without approval from your licensed healthcare professional. We do not guarantee completeness or accuracy and are not liable for any harm resulting from reliance on this material.

See also: Drug Interactions, Side Effects, and Back to top.