Metformin ER Administration Timing
Metformin ER should be administered with the evening meal, not specifically at bedtime, as this is the standard dosing recommendation for once-daily extended-release formulations. 1
Standard Administration Guidelines
- The American Diabetes Association recommends metformin ER be given once daily with the evening meal, allowing for 24-hour glucose control with a single daily dose 1
- The extended-release formulation provides similar efficacy to twice-daily immediate-release metformin at comparable total daily doses, with once-daily dosing improving patient adherence 1
Dosing and Titration Approach
- Initial dosing typically starts at 500 mg once daily with the evening meal to minimize gastrointestinal side effects 1
- Gradual dose titration is recommended, increasing by 500 mg increments every 7 days until the target dose is reached 1
- The maximum effective dose can be up to 1,000-2,000 mg once daily, with most patients achieving good control at these dosages 1
Special Considerations for Timing
- While one older study from 1990 suggested bedtime administration (rather than supper time) might reduce morning hyperglycemia and insulin requirements, this was with older metformin formulations and involved small patient numbers 2
- More recent evidence suggests that morning administration of metformin combined with morning exercise may provide additional glycemic benefits, particularly when metformin is taken before breakfast rather than after 3
- However, the standard recommendation remains evening dosing with the evening meal for metformin ER to optimize 24-hour coverage and minimize gastrointestinal side effects 1
Important Safety Considerations
- Metformin may be temporarily discontinued before procedures using iodinated contrast, during hospitalizations, and when acute illness may compromise renal or liver function 4, 1
- Monitor eGFR at least annually in patients with normal renal function, and every 3-6 months in patients with eGFR <60 mL/min/1.73 m² 1
- For patients with eGFR 30-44 mL/min/1.73 m², reduce the dose to 1,000 mg daily (half the standard dose) 1
Common Pitfalls to Avoid
- Do not administer metformin ER at true "bedtime" (before sleep) as this may increase gastrointestinal side effects and is not the intended dosing schedule 1
- Taking metformin with meals (specifically the evening meal for ER formulations) significantly reduces gastrointestinal adverse effects 5
- If gastrointestinal side effects occur during dose titration, decrease to the previous lower dose and try to advance at a later time 1