TL;DR
- First-line for type 2 diabetes unless contraindicated; lowers glucose by reducing hepatic output and improving sensitivity.
- Start low and titrate to minimize GI side effects; extended-release may be better tolerated.
- Watch B12 over long term; avoid in severe renal impairment and during acute illness with risk of dehydration.
How metformin works
Metformin reduces hepatic glucose production and improves insulin sensitivity in peripheral tissues, lowering fasting and post‑prandial glucose.
Typical dosing and titration
- Immediate‑release: start 500 mg once daily with food, increase to 500 mg twice daily, then up to 1000 mg twice daily as tolerated.
- Extended‑release: start 500–750 mg once daily with evening meal; titrate weekly to a usual max of 2000 mg/day.
Common side effects and tips
- GI: nausea, diarrhea, abdominal discomfort—improve with slow titration and taking with meals.
- Switch to extended‑release if persistent GI effects.
- Long‑term use can lower vitamin B12 levels—consider periodic monitoring.
Safety and contraindications
- Avoid in severe renal impairment (eGFR below product‑specific thresholds) and during acute conditions that increase lactic acidosis risk.
- Hold temporarily for contrast studies or major surgery per local guidance; restart when stable and renal function is adequate.
Disclaimer
This overview is informational and not medical advice. Follow local guidelines and your clinician’s recommendations.
References
- ADA Standards of Care in Diabetes. diabetesjournals.org
- Product labeling for metformin IR and XR. fda.gov