Metformin
Sold as Glucophage, Fortamet, Glumetza
Metformin is the first-line oral medication for type 2 diabetes. It lowers the amount of glucose your liver makes and helps your body respond better to insulin.
What it treats
Type 2 diabetes mellitus, alone or with other diabetes drugs.
Typical dosing
Max dose differs by formulation — do not assume one number: • Immediate-release (IR) — e.g. Glucophage: max 2550 mg/day, given in divided doses (typically 2–3x/day with meals). Usual starting dose 500 mg twice daily, titrated slowly to reduce GI side effects. • Extended-release (XR/ER) — e.g. Glucophage XR, Fortamet, Glumetza: max is generally 2000 mg/day (Glucophage XR label); check the specific product's FDA label, as some ER formulations (e.g. Fortamet) are approved up to 2500 mg/day. Taken once daily, usually with the evening meal.
Monitoring
Kidney function (eGFR) before starting and at least annually (more often if at risk). Metformin is contraindicated at eGFR below 30 mL/min/1.73m² due to lactic-acidosis risk; dose should be reassessed and often reduced at eGFR 30–45. Periodic vitamin B12 levels with long-term use.
Side effects
Common: nausea, diarrhea, gas, metallic taste — usually improves in 1–2 weeks. Rare but serious: lactic acidosis, more likely with kidney impairment, dehydration, or heavy alcohol use. Long-term use can lower vitamin B12 — periodic B12 monitoring is recommended, especially with anemia or neuropathy symptoms.
Interactions to know
Tell your doctor before any imaging study with IV contrast — metformin may need to be held around the procedure. Alcohol increases lactic acidosis risk.
Pregnancy & breastfeeding
Generally considered safe in pregnancy; discuss with your obstetrician.
Clinical content reviewed by the BetterBuyRx clinical team, on 2026-07-07.
Educational only. Not medical advice. Always confirm with your prescriber or pharmacist.