Safety
Boxed warning: lactic acidosis. Post-marketing cases of metformin-associated lactic acidosis have resulted in death. Risk rises with kidney impairment, age 65 or older, contrast imaging, surgery, low oxygen states, heavy alcohol use and liver impairment. Metformin is not for people with an eGFR below 30, and kidney function should be checked before starting. It can lower vitamin B12, and stomach upset and diarrhea are common.
Talk to a licensed clinician about your health history and every medication you take before you start.
Legal status
Prescription only; FDA-approved. Metformin is an FDA-approved generic. Prescribing it for longevity is lawful but off-label: no FDA review has found that it slows aging.
What metformin for longevity is
Approved for type 2 diabetes only. Prescribing it to people without diabetes to slow aging is off-label.
FDA-approved for improving blood sugar control in type 2 diabetes, with diet and exercise.
Dosing
Tablet (immediate or extended release), once or twice a day with meals, as prescribed. Set by your prescriber. Clinics we checked sell 500 mg and 1,000 mg tablets; the MASTERS trial in older adults used 1,700 mg a day.
How well it works
In UKPDS 34 (753 overweight people with type 2 diabetes, median 10.7 years), metformin cut all-cause deaths by 36% compared with diet alone. In people without diabetes, no trial has shown it extends life; the TAME trial was proposed in 2016 to test whether it delays age-related disease. A 2014 UK study found people with diabetes on metformin outlived matched people without diabetes, but a 2022 Danish study of singletons and twins found the opposite. In older adults, metformin blunted gains from aerobic exercise (Konopka 2019) and muscle growth from strength training (MASTERS, 2019). Individual results vary.
Metformin for longevity cost
Prices vary by clinic.