Metformin — Diabetes Drug or Longevity Drug?
The cheapest longevity candidate
Metformin has been used for type 2 diabetes for over 60 years. It's cheap, generic, and has a strong safety record. The longevity interest comes from observational data suggesting diabetic patients on metformin live LONGER than non-diabetic controls — which should not happen by chance.
UKPDS and the observational signal
The 1998 UK Prospective Diabetes Study showed metformin reduced all-cause mortality by 36% and cardiovascular events by 39% in overweight diabetics. A later UK observational study by Bannister (2014) found diabetics on metformin had BETTER survival than matched non-diabetic controls.
But — TAME trial hasn't landed yet
The Targeting Aging with Metformin (TAME) trial, designed specifically to test metformin in non-diabetic older adults for delayed age-related disease, was proposed in 2015. It's still struggling to complete for funding + regulatory reasons. So the question "does metformin work in metabolically healthy people?" is still scientifically open.
The exercise-attenuation finding
A 2019 study (MASTERS trial) showed metformin blunted the muscle-building response to resistance training in older adults. This was unexpected and concerning. It doesn't invalidate metformin for diabetic patients, but it complicates the case for otherwise healthy athletic adults considering it for longevity.
B12 + the lactic-acidosis edge case
Two side effects worth knowing about. (1) Metformin reduces vitamin B12 absorption ~20–30 % over years, so anyone on it long-term should check serum B12 + methylmalonic acid annually and supplement if low. Untreated B12 deficiency mimics dementia. (2) Lactic acidosis is the rare but serious adverse event — risk rises with kidney impairment, severe acute illness, IV-contrast scans (hold metformin around CT scans), and heavy alcohol use. Both are manageable, but neither makes it into most consumer-facing discussion.
Key Takeaway
Metformin is excellent for type 2 diabetes — that's settled. For metabolically healthy adults it's genuinely unclear whether the longevity signal holds AND whether it blunts exercise adaptation enough to matter. Anyone on it long-term should track B12 annually and pause around IV-contrast scans. Attia's stance — "I used to take it, I stopped" — captures where thoughtful practitioners now sit.