Does metformin slow aging? what the trials found

Metformin is a cheap generic that has treated type 2 diabetes for more than 60 years. It became a longevity drug on the strength of observational studies suggesting people who take it live longer, and several online clinics now prescribe it off-label to people without diabetes. The trouble is that the human evidence is mixed, no trial has tested it for aging, and two randomized trials found it can blunt the benefits of exercise.

What metformin is approved for

Metformin is FDA-approved, with diet and exercise, to improve blood sugar control in type 2 diabetes (label). The brand Glucophage has been discontinued, and generic immediate-release and extended-release tablets are sold widely. It isn’t approved to slow aging or prevent disease in people without diabetes, so prescribing it for longevity is off-label. That’s legal; it just means the FDA hasn’t reviewed whether it works for that purpose.

Why it’s studied for aging

The diabetes trial

The strongest data come from people with diabetes. In UKPDS 34, 753 overweight people with newly diagnosed type 2 diabetes were assigned either metformin or conventional treatment, mostly diet, and followed for a median of 10.7 years. Those on metformin had 32% fewer diabetes-related endpoints, 42% fewer diabetes-related deaths and 36% fewer deaths from any cause. That shows metformin helps people with diabetes. It doesn’t show it helps people without diabetes.

The observational studies, which disagree

A 2014 UK study compared 78,241 people with type 2 diabetes who started on metformin with matched people without diabetes. Adjusted median survival was 15% lower in the people without diabetes, suggesting metformin users lived longer than healthy peers. That finding launched much of the interest in metformin for longevity.

The same study included 12,222 people who started on a sulphonylurea, another diabetes drug, and their adjusted median survival was 38% lower than the metformin group’s. The authors read this as support for metformin as first-line diabetes treatment and suggested it “may confer benefit in non-diabetes,” a hypothesis rather than a finding.

A 2022 Danish study tested the same idea in national registers, including twins in which one had diabetes and one didn’t. It found the opposite: people starting metformin for diabetes had higher mortality than people without diabetes, by 32% after adjusting for other illnesses and social factors, and by 64% when compared with their own twin. The authors concluded that metformin monotherapy was not associated with survival equal or superior to the general population, and that the difference from the earlier study was unlikely to come from study design.

Observational studies can’t separate the drug from the people who take it, which is why neither result settles the question.

The trial that was proposed

In 2016, researchers proposed TAME (Targeting Aging with Metformin), a trial designed to test whether metformin delays age-related diseases in older adults without diabetes. TAME was framed as the first step toward drugs that target aging itself. Until a trial like it reports, there is no randomized evidence that metformin slows aging.

The exercise problem

Two randomized trials in older adults found that metformin can reduce the benefits of exercise, which matters because exercise is one of the most common healthy-aging habits.

Responses varied from person to person, and the Konopka authors wrote that more research is needed “prior to prescribing metformin to slow aging.”

Safety

The metformin label carries a boxed warning: lactic acidosis. Post-marketing cases have resulted in death. The label lists the risk factors as kidney impairment, certain other drugs, age 65 or older, imaging with contrast dye, surgery and other procedures, low-oxygen states, heavy alcohol use and liver impairment.

The label also says:

• Kidney function should be checked before starting and periodically after. Metformin is contraindicated below an eGFR of 30, and starting it isn’t recommended between 30 and 45.
• Metformin can lower vitamin B12. In 29-week trials, about 7% of patients developed subnormal levels; the label recommends checking B12 every 2 to 3 years.
• Stomach upset, diarrhea and nausea are the most common side effects.

On its own, metformin rarely causes low blood sugar, but that changes when it’s combined with insulin or drugs that raise insulin. Tell your prescriber about every medicine you take.

Who shouldn’t take it

The label lists three contraindications: an eGFR below 30, a known allergy to metformin, and acute or chronic metabolic acidosis, including diabetic ketoacidosis. It also tells prescribers to pause metformin around some imaging with iodinated contrast dye, especially in people with reduced kidney function, liver disease, heavy alcohol use or heart failure, and to recheck kidney function afterward. It should be stopped temporarily for surgery that limits food and fluids.

Those rules were written for people with diabetes, who take metformin to control blood sugar. Someone taking it for longevity accepts the same risks without a proven benefit, which is why a kidney test before starting matters even if you feel healthy.

What it costs online

Metformin is the cheapest longevity drug sold online. As of October 2026:

Most clinics sell generic tablets rather than compounded ones, because metformin is a widely available FDA-approved generic; Hone Health describes it as “widely prescribed and FDA-approved.” Extended-release tablets are usually taken once a day with the evening meal and immediate-release tablets with meals, so ask which one you’re getting.

That makes the monthly range $25 to $30 at the 3 clinics that publish a monthly price. See our metformin for longevity page for the drug facts and AgelessRx, Healthspan and Hone Health for each clinic’s terms. Many longevity clinics prescribe metformin alongside rapamycin; we cover that drug in rapamycin for longevity.

Questions to ask a prescriber

• What would metformin do for me specifically, given I don’t have diabetes?
• Will you check my kidney function before I start, and my B12 over time?
• Should I time doses around exercise, given the training trials?
• What side effects should make me stop or call you?
• How will we judge whether it’s worth continuing?

The bottom line

Metformin is safe enough for millions of people with diabetes, and it lowered deaths in a long diabetes trial. For healthy people, though, the longevity case is a hypothesis: the observational studies point in opposite directions, the trial meant to test it hasn’t reported, and in older adults it blunted the gains from exercise. At $25 to $30 a month (as of October 2026) it’s inexpensive, but the right comparison isn’t price; it’s whether a clinician can name a benefit for you that outweighs the risks. For other options, see the longevity hub and our longevity clinic rankings.