Standard Dosing for Type 2 Diabetes
Metformin, typically as metformin hydrochloride (e.g., Glucophage), starts at 500 mg once or twice daily with meals to reduce gastrointestinal upset. Providers increase by 500 mg weekly or 850-1,000 mg every 1-2 weeks, up to a maximum of 2,000-2,550 mg per day divided into 2-3 doses.[1][2]
How Dosing Changes for Immediate-Release vs. Extended-Release
Immediate-release tablets allow flexible dosing: 500-850 mg twice daily or 850 mg once daily initially, max 2,550 mg/day. Extended-release (e.g., Glucophage XR) begins at 500 mg once daily, titrating to 2,000 mg once daily max, often better tolerated.[1][3]
Dosing in Kidney Impairment or Elderly Patients
For eGFR 45-59 mL/min/1.73 m², max 2,000 mg/day; 30-44 mL/min/1.73 m², max 1,000 mg/day. Stop if below 30 mL/min/1.73 m² due to lactic acidosis risk. Elderly start lower (500 mg daily) and monitor closely.[2][4]
Use in Polycystic Ovary Syndrome (PCOS) or Weight Loss
Off-label for PCOS: 500-2,000 mg/day divided doses, titrated slowly. For weight management, similar starting doses but evidence is weaker and not FDA-approved.[1][5]
Missed Dose or Overdose Handling
Take missed dose with next meal if soon after; skip if near next dose—do not double. Overdose (e.g., >5 g) risks lactic acidosis; seek emergency care with symptoms like nausea, hypothermia, or hypotension.[2]
[1]: FDA Label - Glucophage (metformin HCl)
[2]: UpToDate - Metformin: Drug Information
[3]: FDA Label - Glucophage XR
[4]: FDA Guidance - Metformin Use in Renal Impairment
[5]: American College of Obstetricians and Gynecologists - PCOS Guidelines