Starting Dose for Metformin

The recommended starting dose for metformin is 500 mg orally twice a day or 850 mg once a day, given with meals. 1

Initial Dosing Recommendations

For adults, metformin should be initiated at 500 mg twice daily or 850 mg once daily with meals 1
For extended-release (XR) formulations, the typical starting dose is 500 mg once daily, usually with the evening meal 2
For pediatric patients 10 years of age and older, the recommended starting dose is also 500 mg twice daily with meals 1
Starting at a lower dose helps minimize gastrointestinal side effects, which are common with metformin initiation 3

After starting metformin, the dose should be increased gradually based on glycemic control and tolerability 1
For immediate-release formulations, increase by 500 mg weekly or 850 mg every 2 weeks 1
For extended-release formulations, increase by 500 mg increments every 7 days 2
Gradual titration is essential to minimize gastrointestinal side effects 3

The maximum recommended daily dose for adults is 2550 mg, given in divided doses 1
Doses above 2000 mg may be better tolerated when given three times a day with meals 1
For pediatric patients, the maximum daily dose is 2000 mg, given in divided doses twice daily 1
For extended-release formulations, the maximum effective dose is typically 2000 mg once daily 2

Assess renal function prior to initiation of metformin and periodically thereafter 1
Metformin is contraindicated in patients with an eGFR below 30 mL/minute/1.73 m² 1
Initiation is not recommended in patients with an eGFR between 30-45 mL/minute/1.73 m² 1
For patients with eGFR 30-44 mL/minute/1.73 m², a reduced dose of 1000 mg daily (half the standard dose) may be considered if metformin is used 2

Gastrointestinal side effects are common with metformin initiation but can be reduced by starting at a lower dose 3
If gastrointestinal side effects occur during dose titration, decrease to the previous lower dose and try to advance the dose at a later time 2
Metformin may be temporarily discontinued before procedures using iodinated contrast, during hospitalizations, and when acute illness may compromise renal or liver function 3, 1
Periodic testing of vitamin B12 levels should be considered in metformin users, especially those with anemia or peripheral neuropathy 3

Extended-release formulations allow for once-daily dosing, which may improve patient adherence 2
The extended-release formulation provides similar efficacy to twice-daily immediate-release metformin at comparable total daily doses 4
Absorption of metformin XR is slower than immediate-release formulations (time to maximum plasma concentration = 7 versus 3 hours) 4