Maximum Daily Dose of Metformin
The maximum daily dose of metformin is 2550 mg for adults, given in divided doses, with doses above 2000 mg better tolerated when given three times a day with meals. 1
Dosing Guidelines for Adults
- Starting dose: 500 mg orally twice daily or 850 mg once daily with meals
- Titration: Increase by 500 mg weekly or 850 mg every 2 weeks based on glycemic control and tolerability
- Maximum dose: 2550 mg per day in divided doses
- Administration: Doses above 2000 mg are better tolerated when given three times daily with meals 1
Dosing Guidelines for Pediatric Patients
- Starting dose: 500 mg orally twice daily with meals (for patients 10 years and older)
- Titration: Increase by 500 mg weekly based on glycemic control and tolerability
- Maximum dose: 2000 mg per day in divided doses 2, 1
Dosing Adjustments Based on Renal Function
Renal function significantly impacts metformin dosing due to the risk of lactic acidosis:
| eGFR (mL/min/1.73 m²) | Recommendation |
|---|---|
| ≥60 | Standard dosing up to 2550 mg daily; monitor kidney function annually |
| 45-59 | Consider dose reduction; monitor kidney function every 3-6 months |
| 30-44 | Reduce dose by 50% (maximum 1000 mg daily); monitor kidney function every 3-6 months |
| <30 | Contraindicated - do not use metformin |
Formulation Considerations
- Immediate-release (IR): Maximum 2550 mg daily
- Extended-release (ER): Maximum 2000 mg daily 3
- Extended-release formulation may improve GI tolerability and allows once-daily dosing, potentially improving adherence 4
Titration Protocol
- Begin with low-dose metformin (500 mg) taken once or twice per day with meals
- After 5-7 days, if no GI side effects occur, advance to 850 mg or two 500 mg tablets twice daily
- If GI side effects appear, decrease to previous lower dose and try advancing again later
- The maximum effective dose is often 850 mg twice daily, though modestly greater effectiveness has been observed with doses up to 2500 mg/day 2
Important Considerations
Temporary discontinuation is recommended during:
Monitor for vitamin B12 deficiency, especially in patients on metformin for >4 years 3
Gastrointestinal side effects (diarrhea, dyspepsia, flatulence) may limit the dose that can be used 2, 5
For patients with persistent GI intolerance on immediate-release formulation, consider switching to extended-release metformin 4
By following these dosing guidelines and making appropriate adjustments based on renal function, metformin can be used effectively and safely to manage type 2 diabetes while minimizing the risk of adverse effects.