Does Metformin Slow Aging? What the Human Evidence Actually Shows

Metformin is a cheap, decades-old type 2 diabetes drug that many longevity enthusiasts now take hoping to slow aging. The short answer: there is no good evidence that metformin slows aging or extends life in people without diabetes. The early excitement came from a mouse study and a large observational study that later failed to replicate. The best long-term randomized data in people without diabetes, from the Diabetes Prevention Program, found no difference in death rates after about 21 years. Two trials in healthy older adults also found metformin blunted some of the benefits of exercise. Metformin is a valuable prescription drug for diabetes. It is not an established anti-aging treatment, and it isn't approved for that use.

The short answer

In mice, metformin at 0.1% of the diet extended healthspan and lifespan in male mice, while a 1% dose was toxic (Martin-Montalvo et al., Nature Communications, 2013). The NIA's three-site Interventions Testing Program then found metformin alone at the same 0.1% dose did not significantly extend lifespan (Strong et al., Aging Cell, 2016).
A 2014 UK study of 78,241 metformin users reported 15% longer adjusted survival than matched people without diabetes (Bannister et al., 2014). A 2022 Danish replication found the opposite: metformin users had 1.52 times the death rate of matched controls (Keys et al., Int J Epidemiol, 2022).
In the randomized Diabetes Prevention Program, 3,234 adults at high risk of diabetes were followed for a median of 21 years. Metformin did not change all-cause mortality (hazard ratio 0.99) (Lee et al., Diabetes Care, 2021).
In healthy older adults, metformin blunted gains in insulin sensitivity and VO2 max from aerobic training (Konopka et al., 2019) and blunted lean-mass gains from strength training (Walton et al., 2019).
The TAME trial, designed to test metformin against aging-related diseases, has not reported results.
Known risks include stomach upset, vitamin B12 deficiency with long-term use and, rarely, lactic acidosis.

Why metformin became a "longevity drug"

Metformin lowers blood sugar mainly by reducing glucose production in the liver and improving insulin sensitivity. At the cellular level, it acts on energy-sensing pathways such as AMPK and mTOR that are also linked to aging in lab studies (see our guide to the mTOR pathway and aging). In 2016, researchers led by Nir Barzilai proposed using metformin as a "tool to target aging," arguing that it had shown protective effects against several age-related diseases in people and should be tested in a trial called TAME (Targeting Aging with Metformin) (Barzilai et al., Cell Metabolism, 2016).

Three lines of evidence drove the hype: a mouse lifespan study, observational data in people with diabetes, and diabetes-prevention trials. Each looks weaker today than it did a decade ago, as a 2025 review titled "Emerging uncertainty on the anti-aging potential of metformin" lays out (Keys et al., Ageing Research Reviews, 2025).

What the animal studies show

The 2013 mouse study gave male mice metformin from middle age. At 0.1% of the diet, it extended healthspan and lifespan and mimicked some benefits of calorie restriction, such as better physical performance and insulin sensitivity. A tenfold higher dose (1%) was toxic (Martin-Montalvo et al., 2013).

The National Institute on Aging's Interventions Testing Program tests compounds in genetically diverse mice at three sites at once, which makes its results harder to fluke. There, metformin alone at 0.1% of the diet did not significantly extend lifespan. Metformin combined with rapamycin did extend lifespan robustly, but the authors noted the added benefit was suggested only by comparison with earlier rapamycin studies (Strong et al., 2016). For more on that drug, see rapamycin for longevity and skin aging.

What the human evidence shows

The observational study that started it

In 2014, Cardiff researchers compared 78,241 people with type 2 diabetes started on metformin, 12,222 started on a sulfonylurea, and 90,463 matched people without diabetes. After adjustment, median survival was 15% lower in the matched people without diabetes than in the metformin group, and 38% lower in the sulfonylurea group (Bannister et al., Diabetes, Obesity and Metabolism, 2014). The authors wrote that this "implies that metformin may confer benefit in non-diabetes." That line was widely repeated as "metformin users outlive healthy people."

The replication that didn't hold up

Observational studies can't rule out hidden differences between groups. Using Danish national registers and twins, researchers re-tested the claim in 2022. People with type 2 diabetes started on metformin had higher mortality than matched people without diabetes: an incidence rate ratio of 1.52 in singletons and 1.90 in twin pairs, still 1.32 and 1.64 after adjusting for other illnesses and social factors (Keys et al., International Journal of Epidemiology, 2022). The authors concluded that metformin "was not associated with survival equal or superior to that of the general population without diabetes."

The longest randomized trial in people without diabetes

The Diabetes Prevention Program (DPP) randomly assigned 3,234 adults with prediabetes and overweight to placebo, metformin 850 mg twice daily, or an intensive lifestyle program. Over about 2.8 years, metformin cut new diabetes cases by 31% and the lifestyle program by 58% compared with placebo (Knowler et al., NEJM, 2002).

But preventing diabetes isn't the same as slowing aging. After a median of 21 years of follow-up, metformin did not affect death from all causes (HR 0.99, 95% CI 0.79–1.25), cancer (HR 1.04) or cardiovascular disease (HR 1.08). The lifestyle program didn't change mortality either (Lee et al., Diabetes Care, 2021). This is the closest thing we have to a long-term, randomized test of metformin in people without diabetes, and it found no survival benefit.

Tissue studies in older adults

In a small crossover trial, 14 adults around age 70 took metformin and placebo for 6 weeks each. Metformin changed the activity of 647 genes in muscle and 146 in fat tissue, including pathways tied to metabolism and DNA repair (Kulkarni et al., Aging Cell, 2018). Gene expression changes are interesting biology, but they don't show that people live longer or age more slowly.

The exercise trade-off

Exercise is one of the best-proven ways to stay healthy as you age (see exercise and anti-aging). Two randomized, double-blind trials suggest metformin can get in its way:

Trial	Who and what	Result with metformin
Konopka 2019	53 adults, avg. age 62, 12 weeks of aerobic training	Smaller gains in insulin sensitivity and VO2 max
MASTERS 2019	94 adults 65+, 14 weeks of strength training	Placebo gained more lean mass and thigh muscle

In the aerobic study, metformin also "abrogated the exercise-mediated increase in skeletal muscle mitochondrial respiration," and the authors cautioned that more research is needed "prior to prescribing metformin to slow aging" (Konopka et al., Aging Cell, 2019). In the MASTERS trial, participants took 1,700 mg a day, and the authors concluded that metformin "negatively impacts the hypertrophic response to resistance training in healthy older individuals" (Walton et al., Aging Cell, 2019). Keeping muscle matters as you age, so this trade-off is a real concern for healthy people who exercise.

What about the TAME trial?

TAME was designed as a multi-site, placebo-controlled trial in older adults without diabetes. It would test whether metformin delays a group of age-related outcomes such as heart disease, cancer, dementia and death, rather than any single disease (Barzilai et al., 2016; AFAR). The idea is important because regulators don't treat aging itself as a condition a drug can be approved for. But TAME has not reported any results, and when we searched ClinicalTrials.gov in October 2026, we could not find a registration for it. Until results exist, TAME is a plan, not evidence.

Does metformin help skin aging?

People searching "metformin anti-aging" are often thinking about wrinkles. We found no randomized trials showing that oral metformin reduces wrinkles or visibly improves aging skin in people. Its potential relevance to skin is indirect: high blood sugar can speed up collagen damage through glycation, and metformin lowers blood sugar in people with diabetes or insulin resistance. For people with conditions such as PCOS, a doctor may prescribe metformin for metabolic reasons. That's a medical decision, not a skincare one. For visible skin aging, sunscreen, retinoids and proven in-office treatments have far stronger evidence.

Side effects and risks

Metformin has a long safety record when it's prescribed and monitored. It still has real side effects:

Stomach problems: diarrhea, nausea, stomach discomfort and gas are common, especially when starting (MedlinePlus).
Vitamin B12 deficiency: in the DPP Outcomes Study, low or borderline-low B12 was more common with metformin at 5 years (19.1% vs 9.5%) and 13 years (20.3% vs 15.6%), and each year of use raised the odds of deficiency by about 13% (Aroda et al., JCEM, 2016). The authors suggested routine B12 testing in people on metformin.
Lactic acidosis: a rare but life-threatening complication, carried as an important warning on the label. Kidney disease, heavy drinking, serious illness, dehydration and contrast dye for imaging can raise the risk (MedlinePlus).
Blunted exercise gains: as described above, in healthy older adults.

Metformin is prescription-only in the US. Buying it online without a prescription or taking it "for longevity" without medical supervision skips the kidney checks and monitoring the label calls for.

Metformin vs proven healthy-aging habits

Approach	Human evidence for healthy aging	Notes
Metformin (no diabetes)	No survival benefit in 21-year RCT follow-up	Prescription only; may blunt exercise gains
Regular exercise	Strong	Builds muscle, fitness and insulin sensitivity
Lifestyle weight loss	Cut diabetes risk 58% in the DPP	Outperformed metformin for prevention

How to think about metformin for longevity

If you have type 2 diabetes or prediabetes, metformin may be a good option. That's a conversation for your doctor, based on your blood sugar, kidney function and other health factors.
If you're healthy and want to slow aging, current human evidence doesn't support taking metformin for that purpose.
If you exercise to stay strong, know that two trials found metformin blunted training gains in older adults.
Watch for new evidence, but judge it by randomized trials that measure real outcomes, such as disease, disability and death, not mouse lifespan or biomarkers alone.
Put your effort where evidence is strongest: exercise, not smoking, sleep, a healthy weight, blood pressure and blood sugar control, and sun protection for your skin. See epigenetic clocks and biological age for why "aging biomarkers" are tricky to interpret.

Frequently asked questions

Does metformin slow aging in humans?

There's no good evidence that it does in people without diabetes. In the randomized Diabetes Prevention Program, metformin didn't change death rates over a median of 21 years (hazard ratio 0.99), and no trial has shown it slows aging.

Do people taking metformin live longer than people without diabetes?

A 2014 UK study suggested that, reporting 15% longer survival in metformin users than matched controls without diabetes. A 2022 Danish study using national registers and twins found the opposite, with metformin users dying at about 1.5 times the rate of matched controls.

Does metformin extend lifespan in mice?

One 2013 study found a low dose extended lifespan in male mice. The NIA's larger three-site Interventions Testing Program found metformin alone did not significantly extend mouse lifespan, although metformin combined with rapamycin did.

What is the TAME trial?

TAME (Targeting Aging with Metformin) is a proposed placebo-controlled trial in older adults without diabetes. It would test whether metformin delays a cluster of age-related diseases and death. It has not reported any results.

Does metformin reduce wrinkles?

We found no randomized trials showing that oral metformin reduces wrinkles or visibly improves skin aging. Sunscreen, retinoids and proven in-office treatments have much stronger evidence for skin.

Can metformin interfere with exercise?

In two randomized trials in healthy older adults, metformin blunted improvements in insulin sensitivity and VO2 max from aerobic training and reduced lean-mass gains from strength training compared with placebo.

What are the side effects of metformin?

Common side effects include diarrhea, nausea and stomach upset. Long-term use is linked to vitamin B12 deficiency. Lactic acidosis is rare but serious, and the risk is higher with kidney disease or heavy drinking.

Bottom line

Metformin is an excellent, inexpensive diabetes drug, and it was reasonable to wonder whether it might slow aging. But the evidence has moved the wrong way: the key mouse result didn't replicate in the NIA's testing program, the famous observational survival advantage didn't replicate in Danish data, the longest randomized follow-up in people without diabetes found no effect on mortality, and trials in healthy older adults showed it can blunt exercise benefits. Until a trial like TAME reports positive results, metformin isn't an anti-aging treatment for healthy people. If you're curious about it, talk to your doctor rather than sourcing it yourself.

This article is for educational purposes only and is not medical advice. Metformin is a prescription medicine. Talk to your doctor before starting or stopping any medication, especially if you have kidney or liver disease, drink alcohol heavily, or take other medicines.