The most common dose of metformin for adults with type 2 diabetes falls between 1,500 and 2,000 mg per day, split into two or three doses. But getting there takes time. Prescribers almost always start low and increase gradually to reduce the stomach side effects metformin is known for.
Starting Dose for Adults
Most adults begin at 500 mg once or twice daily, taken with meals. From there, the dose increases by 500 mg every one to two weeks until blood sugar is well controlled or the target dose is reached. This slow ramp-up matters because metformin commonly causes nausea, diarrhea, and stomach discomfort early on, and your body needs time to adjust.
Extended-release tablets, which dissolve more slowly, are available in 500 mg and 1,000 mg strengths. These are taken once daily, usually with dinner, and tend to cause fewer digestive issues than the immediate-release version. Immediate-release tablets come in 500 mg, 850 mg, and 1,000 mg strengths.
Maximum Daily Dose
For immediate-release metformin, the maximum is 2,550 mg per day (typically 850 mg three times daily). For extended-release formulations, the ceiling is generally 2,000 mg per day. Most people land somewhere between 1,500 and 2,000 mg daily, which is the range where metformin delivers most of its blood-sugar-lowering benefit without a steep increase in side effects.
Going above 2,000 mg doesn’t always translate into meaningfully better blood sugar control for every person, so your prescriber will weigh whether the extra dose is worth the added stomach trouble.
Doses for Children and Teens
Metformin is approved for children aged 10 and older with type 2 diabetes. The starting dose is lower, typically 250 to 500 mg per day, with weekly increases. The maximum for pediatric patients is 1,000 mg twice daily or 850 mg three times daily, depending on the formulation. The same gradual approach applies: slow increases give a child’s digestive system time to adapt.
Dosing for PCOS
Metformin is also widely prescribed off-label for polycystic ovary syndrome, where it helps improve insulin sensitivity and can restore more regular menstrual cycles. The 2023 international evidence-based guidelines for PCOS recommend titrating up to between 1,000 and 2,500 mg daily in adults, with a suggested maximum of 2,500 mg. For adolescents with PCOS, the recommended cap is 2,000 mg per day.
The same start-low strategy applies here: begin with 500 mg and add 500 mg every one to two weeks. Extended-release tablets are specifically recommended in the PCOS guidelines to minimize side effects and help people stick with the medication long term.
How Kidney Function Changes the Dose
Your kidneys clear metformin from your body, so reduced kidney function means the drug can build up to unsafe levels. Prescribers use a blood test called eGFR (estimated glomerular filtration rate) to gauge how well your kidneys are filtering. The thresholds work like this:
- eGFR above 60: Full dosing up to 2,550 mg daily is considered safe.
- eGFR 45 to 59: The maximum drops to 2,000 mg per day.
- eGFR 30 to 44: No more than 1,000 mg per day, and metformin should not be started new at this level.
- eGFR below 30: Metformin is not recommended at all.
If you’re already on metformin and your kidney function declines, your prescriber will likely reduce the dose in steps rather than stop it abruptly. Kidney function is typically rechecked at least once a year for anyone taking metformin, and more frequently if levels are borderline.
Why the Dose Gets Split Up
Immediate-release metformin is usually divided into two or three doses across the day because a single large dose is harder on the stomach and produces a sharper spike in blood levels. Taking it with food slows absorption and reduces nausea. Extended-release versions solve this problem by design, releasing the medication slowly enough that once-daily dosing works well for most people.
If you’ve been prescribed immediate-release tablets and stomach side effects are making it hard to stay on the medication, switching to the extended-release form at the same total daily dose is a common and effective fix.
What Happens if You Miss a Dose
Metformin has a relatively short active window in your body, roughly 6 to 12 hours depending on the formulation. If you miss a dose, take it as soon as you remember, unless it’s nearly time for your next dose. Doubling up to compensate increases the risk of stomach problems without meaningful benefit. One missed dose won’t dramatically change your blood sugar control, but consistently missed doses will.