What it means
Metformin is a biguanide, derived from a compound in French lilac, and the first-line drug for type 2 diabetes worldwide. It lowers glucose output from the liver, improves insulin sensitivity and activates AMPK, partly by mildly inhibiting mitochondrial complex I. It also changes the gut-microbiome and lowers IGF-1 slightly.
In longevity circles it is taken by non-diabetics at 500–1,500 mg per day on the strength of observational data and its mechanism.
Why it matters for longevity
If a safe, generic drug lowered the incidence of several age-related diseases at once, it would reshape preventive medicine. That is the premise of the TAME trial (Targeting Aging with Metformin), designed to test exactly that in 3,000 older adults. Metformin's real importance may be as the proof-of-concept that ageing can be a drug target at all.
What the evidence says
The cohort claim that diabetics on metformin outlived non-diabetics (Bannister 2014) has not survived scrutiny: a 2022 reanalysis found the result driven by survivor bias and by comparison with sulfonylurea users. In the mouse ITP, metformin alone did not extend lifespan; combined with rapamycin it added a little. In diabetics it reduces cardiovascular events and some cancers, which is well established.
The MASTERS trial (Konopka 2019): 53 healthy older adults, metformin or placebo during twelve weeks of aerobic training. Metformin blunted the gains in VO2max, insulin sensitivity and mitochondrial respiration — about half the training benefit was lost. A 2022 follow-up found the same for strength training. TAME has struggled for funding and has not reported.
How to measure or use it
- Prescription-only. The case for it in a non-diabetic is strongest with HbA1c in the prediabetic range (5.7–6.4%) or a high HOMA-IR that lifestyle has not fixed.
- Watch vitamin B12 (metformin lowers absorption), kidney function (as cystatin C) and the training response.
- If training is a central part of the plan, the MASTERS result argues for fixing metabolic markers with the training first.
Related
- The longevity drugs — the full case for and against
- Metabolic health — the markers it moves
- VO2max and longevity — what MASTERS put at risk
Frequently asked questions
Should a healthy person take metformin for longevity?
The evidence does not support it: the lifespan cohort result did not replicate, the mouse data are negative alone, and it blunts training gains.
What did the TAME trial find?
It has not yet reported. It is designed to test whether metformin delays the onset of age-related diseases in 3,000 older non-diabetic adults.
Does metformin cause B12 deficiency?
It lowers B12 absorption; deficiency is common after years of use. Yearly B12 testing is standard.
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