Head-to-head

Metformin vs Rapamycin

Two prescription drugs borrowed for longevity from opposite ends of biology: an old, cheap diabetes tablet versus a transplant immunosuppressant with the field's best animal lifespan data.

Metformin

Clinical data

An approved diabetes drug with an intriguing longevity hypothesis — but the dedicated aging trial (TAME) is still pending; longevity in healthy people is unproven.

Full Metformin evidence review

Rapamycin

Clinical data

Extends lifespan in mice via mTOR; small human trials (PEARL) address safety, but a longevity benefit in people is unproven.

Full Rapamycin evidence review

Side by side

	Metformin	Rapamycin
Marketed for	Longevity, healthspan, metabolic aging	Longevity, healthspan (off-label)
Evidence grade	Clinical data	Clinical data
Family	Metabolic / AMPK	mTOR & other
Key human source	MILES/TAME rationale 2014	mTOR/mouse lifespan, Nature 2009

marks a row where the two differ. Evidence grades come from our evidence matrix, which grades each molecule on the human data for the use it is marketed for.

Our verdict

Neither is approved for aging; both are taken off-label for it, and they have never been compared head to head. Metformin's longevity case is an observational survival signal plus MILES, which measured gene-expression changes in muscle and fat rather than any clinical outcome, with TAME, the trial designed to settle the question, still not reported. Rapamycin has the stronger biology, extending lifespan in genetically heterogeneous mice even when started late in life, and PEARL found one year of intermittent dosing generally well-tolerated with modest, mixed healthspan results. It also carries the heavier risk: sirolimus is an immunosuppressant, and the infection risk, impaired wound healing, and lipid and glucose effects on its label come from daily transplant dosing.

Metformin fits if

Metformin is the more conservative off-label choice for someone who has a metabolic reason to be on it anyway and accepts that the longevity claim rests on observational and surrogate data.

Rapamycin fits if

Rapamycin fits only someone working with a physician who wants the strongest animal lifespan evidence in the field and understands it is an immunosuppressant with no proven human aging benefit.