Metformin Initiation and Dosing Guidelines

Initial Dosing – Immediate‑Release Formulation

The recommended starting dose of immediate‑release metformin is 500 mg taken twice daily or 850 mg taken once daily with meals in adults. 1

For the extended‑release formulation, the initial dose is 500 mg once daily taken with a meal. 1

The dose should be increased by 500 mg each day every 7 days until the maximum recommended dose is reached. 1

eGFR ≥ 60 mL/min/1.73 m²: Standard starting dose (500 mg twice daily or 850 mg once daily) may be used. 1, 2
eGFR 45–59 mL/min/1.73 m²: Begin with half the standard dose and titrate up to half of the maximum recommended dose. 2, 1
eGFR 30–44 mL/min/1.73 m²: Same approach as the 45–59 group—start at half the standard dose and titrate to half the maximum dose. 2, 1
eGFR < 30 mL/min/1.73 m²: Metformin is contraindicated; it should not be initiated. 1

Initiating therapy with a low dose and gradually titrating upward reduces the incidence of gastrointestinal side effects. 3
If gastrointestinal symptoms develop during titration, the dose should be reduced to the last tolerated level before attempting further increases. 3
Taking metformin with meals significantly lowers the risk of gastrointestinal adverse events. 4
The extended‑release formulation may provide better gastrointestinal tolerability in some patients. 4

Baseline and periodic eGFR assessment is required before starting metformin and throughout therapy. 1
When eGFR is < 60 mL/min/1.73 m², monitoring frequency should be increased to every 3–6 months (instead of annually). 1
Vitamin B12 levels should be checked in patients who have been on metformin for more than 4 years. 1