Metformin dosage
Metformin doses are set and adjusted by a prescriber, not self-titrated. The FDA label gives a starting dose and a maximum, but the dose that fits you depends on your blood sugar response, how your stomach tolerates it, and — most importantly — your kidney function. This page is a plain-language reference to what the label actually says, not a dosing instruction.
This is reference, not a dosing instruction. Metforminis prescription-only and the dose is individualized and titrated by a prescriber to your condition, response, kidney/liver function and other medicines. The figures below are the FDA label’s — do not start, change or stop a dose based on this page.
Approved for: FDA-approved as an adjunct to diet and exercise to improve glycemic control in adults and children 10 years and older with type 2 diabetes mellitus. Immediate-release is approved down to age 10; the extended-release tablets are approved for adults. Metformin is not used for type 1 diabetes.
Available as: Immediate-release tablets: 500 mg, 850 mg, and 1,000 mg. Extended-release tablets: 500 mg and 1,000 mg. (Some manufacturers also make an oral solution and alternative extended-release forms.)
| Use | What the label says |
|---|---|
| Type 2 diabetes (immediate-release) | Label starting dose: "The recommended starting dose of metformin hydrochloride tablets are 500 mg orally twice a day or 850 mg once a day, given with meals." Titrate slowly: "Increase the dose in increments of 500 mg weekly or 850 mg every 2 weeks on the basis of glycemic control and tolerability, up to a maximum dose of 2550 mg per day, given in divided doses." Doses above 2,000 mg/day may be better tolerated split three times a day with meals. (Pediatric patients 10 years and older: start 500 mg twice daily, maximum 2,000 mg/day.) |
| Type 2 diabetes (extended-release) | Label: "The starting dose of metformin hydrochloride extended-release tablets in patients who are not currently taking metformin is 500 mg orally, once daily with the evening meal. Increase the dose in 500 mg increments every 1 to 2 weeks" — "while not exceeding the maximum recommended daily dose of 2,000 mg." If control is not reached on 2,000 mg once daily, the label notes a trial of 1,000 mg twice a day. Extended-release is for adults. |
Maximum dose
The immediate-release ceiling is 2,550 mg/day — the label titrates "up to a maximum dose of 2550 mg per day, given in divided doses." The extended-release ceiling is lower at 2,000 mg/day: "while not exceeding the maximum recommended daily dose of 2,000 mg." These are label maximums, not targets — many people are controlled below them, and the effective dose is whatever a prescriber titrates you to against blood sugar and tolerance.
Dose adjustments
Kidney function sets the hard limits, and the label requires checking eGFR before starting and at least yearly. Contraindicated below eGFR 30: "Metformin hydrochloride tablets are contraindicated in patients with an eGFR less than 30 mL/min/1.73 m2." Do not start between 30 and 45: "Initiation of metformin hydrochloride tablets is not recommended in patients with eGFR between 30 to 45 mL/min/1.73 m2." Iodinated-contrast hold: "Discontinue metformin hydrochloride tablets at the time of, or prior to, an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/min/1.73 m2," then recheck kidney function after 48 hours before restarting. Elderly: because kidney function declines with age and drives the lactic-acidosis risk, the label calls for assessing renal function before and during treatment and dosing conservatively in older patients.
Dosing safety — read before you rely on any number
BOXED WARNING — lactic acidosis: "Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias." It is rare but fatal in roughly half of cases, and onset is subtle — "malaise, myalgias, respiratory distress, somnolence, and abdominal pain." Label-named risk factors include renal impairment, age 65 and older, iodinated contrast, excessive alcohol, and heart or liver failure: "If metformin-associated lactic acidosis is suspected, immediately discontinue metformin hydrochloride tablets and institute general supportive measures in a hospital setting. Prompt hemodialysis is recommended." Take doses with meals and titrate slowly to blunt GI upset. Long-term use can lower vitamin B12: "Measure hematologic parameters on an annual basis and vitamin B12 at 2 to 3 year intervals in patients on metformin hydrochloride tablets and manage any abnormalities."
Bottom line
Treat this as a reference, not a prescription. Metformin is titrated by a clinician from a low starting dose upward against your blood sugar, GI tolerance, and kidney function — and an eGFR under 30 is an absolute stop. Do not change your own dose, and do not restart after a contrast scan, without your prescriber.
Frequently asked questions
What is the maximum dose of metformin?
For immediate-release metformin the FDA label maximum is 2,550 mg per day, given in divided doses. For the extended-release tablets it is lower, 2,000 mg per day. Most people are well controlled below these ceilings — the maximum is a label limit, not a target.
What is the starting dose of metformin?
The immediate-release label starts at 500 mg twice a day or 850 mg once a day, taken with meals. The extended-release starts at 500 mg once daily with the evening meal. A prescriber then raises the dose gradually, usually every 1 to 2 weeks, based on blood sugar and how you tolerate it.
Should I take metformin with food?
Yes. The label directs immediate-release doses to be taken with meals and extended-release with the evening meal. Taking it with food and increasing the dose slowly reduces the nausea, diarrhea, and stomach upset that are common in the first weeks.
What is the difference between metformin ER and IR dosing?
Immediate-release (IR) is taken 2 to 3 times a day with meals and can go up to 2,550 mg/day. Extended-release (ER/XR) is taken once daily with the evening meal and tops out at 2,000 mg/day; if that is not enough, the label allows a trial of 1,000 mg twice daily. Same drug, different release profile and different ceilings.
Can I take metformin with kidney disease?
It depends on your eGFR. The label contraindicates metformin below an eGFR of 30 mL/min/1.73 m2, does not recommend starting it when eGFR is 30 to 45, and says to hold it around iodinated-contrast imaging when eGFR is 30 to 60. Impaired kidneys are the main driver of the lactic-acidosis boxed warning, so this is a clinician's call from your lab values.
What should I do if I miss a dose of metformin?
Per MedlinePlus, take the missed dose as soon as you remember — but if it is almost time for the next dose, skip it and continue your regular schedule. Do not take a double dose to make up for a missed one. If you miss doses often, ask your prescriber instead of changing the schedule yourself.
Sources
More guides for Metformin
Other dosage guides: Amoxicillin dosage · Prednisone dosage · Gabapentin dosage · Ibuprofen dosage · Lisinopril dosage · Levothyroxine dosage · Omeprazole dosage · Doxycycline dosage · Ondansetron dosage · Albuterol dosage · Allopurinol dosage · Methotrexate dosage · Alendronate dosage · Fluconazole dosage · Acetaminophen dosage · Diphenhydramine dosage · Naproxen dosage · Aspirin dosage · Cetirizine dosage · Dimenhydrinate dosage · Famotidine dosage.
Doses are transcribed from the FDA-approved label and are general reference information, not medical advice or a personal dose. Only a prescriber can set or change your dose. If you think you took too much, contact Poison Control (1-800-222-1222) or 911.