Sirolimus vs metformin for longevity: what the evidence says

Last updated 2026-07-27

Are rapamycin and metformin actually competing for the same job?

Sort of, but they're not really doing the same thing biologically. Rapamycin (sirolimus) directly inhibits mTOR, the nutrient-sensing kinase that sits at the center of the geroscience hypothesis, the idea that one pathway drives multiple age-related diseases at once ^[1]. Metformin works upstream and diffusely: it activates AMPK, lowers hepatic glucose output, and has secondary effects on mTOR signaling, but it wasn't built or discovered as an mTOR drug. It's a 60-year-old type 2 diabetes medication. People lump them together because both got picked up by the longevity crowd as cheap, generic, already-approved drugs with plausible aging biology behind them. That's a fair reason to compare them. It's not a reason to assume they're interchangeable. If you're choosing between them for an off-label longevity protocol, you're really choosing between two different bets: a strong animal signal with a thin human safety record at longevity doses (rapamycin), versus a weak-to-mixed animal signal with a deep human safety record at diabetes doses (metformin). Sirolimus and rapamycin are the same molecule, just two names, one from the original Rapamune brand chemistry and one used in research literature. That matters here because a lot of dosing and mouse-study literature says "rapamycin" while prescriptions in the US say "sirolimus."

What does the mouse data actually show for each drug?

This is where the two drugs really split apart. The National Institute on Aging's Interventions Testing Program (ITP) has tested both, across three labs, with genetically heterogeneous mice, which is about as rigorous as rodent lifespan science gets. Rapamycin extended median lifespan in both sexes, in multiple independent cohorts, starting at different ages. The original 2009 Nature paper found rapamycin, started at 600 days of age (roughly a 60-year-old human equivalent), extended female median lifespan by 13% and male median lifespan by 9% ^[2]. A later ITP paper testing rapamycin started at 9 months found effects up to 23% in females and 26% in one male cohort at higher doses, with a clear dose-response relationship ^[1]. The effect has replicated enough times across labs that geroscientists treat it as close to a settled finding in mice, which is unusual. Metformin's mouse data is much less consistent. The ITP tested metformin alone and found no significant lifespan extension in mice; a combination of metformin plus rapamycin extended lifespan more than metformin alone, but not more than rapamycin alone, in the reported ITP results ^[1]. Some earlier, smaller studies (Anisimov and colleagues, and the widely cited Martin-Montalvo 2013 Nature Communications paper) reported lifespan extension in specific mouse strains at specific doses, but the ITP's larger, better-controlled testing didn't reproduce a metformin-alone benefit ^[1]. That's a meaningful gap between the two drugs' animal evidence. | Measure | Rapamycin (ITP) | Metformin (ITP) |

Has either drug been tested for lifespan extension in humans?

No, neither one has a completed human trial that measured lifespan or healthspan as a primary outcome, and this is the single most important fact in this whole comparison. Metformin got closer to having a dedicated aging trial. TAME (Targeting Aging with Metformin) was designed by a group led by Dr. Nir Barzilai and colleagues as a roughly 3,000-person, six-year trial to see if metformin delayed a composite of age-related diseases (cardiovascular disease, cancer, dementia, mortality) in people without diabetes. As of the most recent public updates from the TAME organizers, the trial has not secured full funding and has not enrolled and completed as originally planned; it remains a proposed and partially funded trial design rather than a finished study. People sometimes cite TAME as though it already reported longevity results. It hasn't. Rapamycin has no equivalent human aging trial at all, not even a proposed, partially-funded one at TAME's scale. What exists instead is a scatter of small human studies: a 2014 Novartis-funded trial (Mannick et al., Science Translational Medicine) found that a rapamycin analog (everolimus) improved influenza vaccine response in elderly subjects, which is an immune biomarker study, not a lifespan study ^[3]. There are also small studies and ongoing efforts like the PEARL trial looking at low-dose intermittent rapamycin in healthy older adults for safety and biomarker signals, not mortality ^[4]. None of this is a finished, adequately powered human lifespan or healthspan trial for either drug. So if someone tells you rapamycin or metformin is "proven to extend human lifespan," that's not an accurate statement of where the science stands, for either drug.

How do the off-label dosing protocols actually differ?

The two drugs are used completely differently in longevity protocols, which is another reason the comparison isn't apples to apples. Metformin is typically dosed daily, similarly to how it's used for diabetes, often 500 to 1500 mg per day, sometimes split into two doses to reduce GI side effects. It's continuous dosing, no cycling. Rapamycin, in the off-label longevity context, is almost always dosed intermittently, not daily. This comes directly from the mouse pharmacology: intermittent high-dose pulses seem to hit mTORC1 (the target associated with the beneficial effects) while sparing mTORC2 (associated with the metabolic side effects) more than continuous daily dosing does. Common human protocols floating around clinical practice use once-weekly or once-every-two-weeks dosing, often in the 3 to 10mg range depending on body weight, though there's no FDA-approved dose for this indication because there is no approved indication. If you're actually starting a protocol, Sirolimus Rx dosage and a dosage calculator walk through how clinicians commonly think about weight-based intermittent dosing, and cycle length covers how on/off schedules are typically structured. None of that is FDA guidance; it's off-label practice patterns. Worth repeating: rapamycin is FDA-approved, but only for organ transplant rejection prophylaxis, and separately as Fyarro (albumin-bound sirolimus) for a rare tumor called malignant PEComa, and as topical Hyftor for facial angiofibromas in tuberous sclerosis ^[5] . None of those approvals cover aging, longevity, or healthy adults. Every longevity use of sirolimus is off-label.

What are the real side effect risks for each drug?

Metformin's side effect profile is well characterized after decades of diabetes use: GI upset (diarrhea, nausea, metallic taste) in a meaningful minority of users, and a rare but serious risk of lactic acidosis, mostly in people with significant kidney impairment . The FDA label specifically restricts use based on kidney function (eGFR) for this reason . It also can modestly lower vitamin B12 levels with long-term use. Rapamycin's risk profile at transplant doses (continuous daily dosing, combined with other immunosuppressants) is well documented and includes immunosuppression with higher infection risk, delayed wound healing, elevated lipids, mouth ulcers (stomatitis) in a substantial fraction of patients, and increased risk of certain cancers over long-term continuous use, per the FDA-approved prescribing information . What's genuinely uncertain is how much of that risk profile carries over to low-dose, intermittent, weekly dosing in otherwise healthy people, since that's not the population or dosing pattern the FDA safety data comes from. Mouth ulcers are the side effect reported most consistently even at intermittent low doses in the people who use these protocols; some degree of impaired immune response (worse or slower response to infections) is a real theoretical and reported concern given the mechanism, even if the magnitude at low intermittent doses looks smaller than at transplant doses. Metabolic effects, including changes in lipids and blood glucose, have also been reported at some intermittent doses. Anyone starting sirolimus should be working with a clinician who monitors labs and understands the injection or dosing logistics; see how to reconstitute Sirolimus Rx, how to inject, and injection sites for the practical mechanics, though those pages describe procedure, not proof of longevity benefit. Metformin doesn't carry the immunosuppression risk at all. That's a genuine, meaningful safety advantage in metformin's favor if immune function is your top concern.

Can you take rapamycin and metformin together?

Some longevity-focused prescribers do combine them, on the logic that they hit overlapping but distinct pathways (mTOR and AMPK), and the ITP's own combination data found that rapamycin plus metformin extended mouse lifespan somewhat more than metformin alone, though not clearly more than rapamycin alone ^[1]. There's no dedicated human safety data on the combination at longevity doses, and no dedicated human lifespan data on the combination at all. Combining two off-label drugs multiplies the unknowns rather than the certainties. If you're going to combine them, that's a conversation for a prescriber who is tracking your labs (kidney function, lipids, blood glucose, complete blood count) over time, not a decision to make from a forum post.

Which one actually has better evidence: rapamycin or metformin?

For animal lifespan data specifically, rapamycin's evidence is stronger, more replicated, and shows a clearer dose-response than metformin's ^{[2] [1] [1]}. That's a fairly uncontroversial statement inside the geroscience field at this point. For human evidence, neither drug wins, because neither has finished a human aging trial. Metformin has the deeper overall human safety record, just not for aging; that record comes from decades of diabetes use in millions of patients . Rapamycin's human safety record is real but narrower: it comes mostly from transplant patients on continuous dosing combined with other immunosuppressants, a very different population and dosing pattern than a healthy 50-year-old taking it once a week . So the honest summary is: rapamycin wins on animal efficacy data, metformin wins on human safety familiarity, and both are tied at zero on completed human longevity trials. Anyone telling you one of these drugs is "proven" for human lifespan extension is overstating the evidence, whichever drug they're talking about.

Does cost or access differ meaningfully between them?

Metformin is cheap and extremely available; it's a generic diabetes drug carried by essentially every pharmacy, typically costing single-digit to low double-digit dollars per month out of pocket without insurance, and often less on a pharmacy discount program. Sirolimus/rapamycin generic tablets and oral solution are also generic and have been for years, but off-label longevity dosing (particularly compounded formulations, specific low-dose tablet strengths, or injectable-style protocols marketed for longevity use) typically runs higher, and pricing varies a lot depending on pharmacy, dose, and whether it's obtained through a standard retail pharmacy versus a specialty or compounding pharmacy working with a longevity-focused prescriber. If you're evaluating the off-label route, working through a provider-reviewed pathway matters more for sirolimus than for metformin, because the dosing, monitoring, and formulation questions are genuinely more complex; Sirolimus Rx connects patients with clinicians who prescribe within that framework, with prescriptions filled through licensed pharmacy partners, which is a meaningfully different path than buying research-chemical sirolimus online with no clinician involved.

So which should a longevity researcher actually watch or use?

If you're a researcher tracking the field rather than a patient making a decision, the honest position is this: rapamycin has the stronger biological rationale and the stronger animal data, but it also carries the more novel, less-tested human risk profile at the doses people are actually using off-label. Metformin has a weaker mouse signal and an unfunded human aging trial (TAME), but decades of human safety data at its standard dose. If you're a patient weighing this for yourself, that's a decision to make with a clinician, not from an internet comparison, because it depends on your kidney function, your infection risk, your cancer history, and what you're actually trying to achieve. Nobody, including the researchers running these trials, has a completed human dataset that tells you whether either drug extends human lifespan. That's not a caveat tacked onto the end of the story; for both of these drugs, it is the story.

Frequently asked questions

Is rapamycin the same as metformin?

No, they're different molecules with different mechanisms. Rapamycin (sirolimus) directly inhibits mTOR. Metformin activates AMPK and lowers glucose production in the liver, with secondary, less direct effects on mTOR signaling. They're often discussed together because both are cheap generics being explored off-label for longevity.

Is sirolimus the same drug as rapamycin?

Yes. Sirolimus and rapamycin are the same molecule; sirolimus is the generic drug name used in US prescribing, while rapamycin is the name used more often in scientific literature and by the original discoverers. Prescriptions and FDA labeling use sirolimus.

Has metformin been proven to extend human lifespan?

No. The trial designed to test this, TAME (Targeting Aging with Metformin), has not been fully funded or completed as of the most recent public updates from its organizers. No completed, adequately powered human trial has shown metformin extends human lifespan.

Has rapamycin been proven to extend human lifespan?

No. Rapamycin's lifespan extension data comes from mouse studies, primarily the NIA Interventions Testing Program, which has replicated the effect across multiple cohorts and labs. There is no completed human trial measuring rapamycin's effect on human lifespan or mortality.

Why do people compare rapamycin and metformin for longevity if they're different drugs?

Both are cheap, generic, already-FDA-approved drugs (for transplant rejection and type 2 diabetes respectively) with plausible aging-related mechanisms, which made them the two most accessible candidates for off-label longevity use before any purpose-built anti-aging drug exists.

Which has stronger mouse data, rapamycin or metformin?

Rapamycin. The NIA's Interventions Testing Program found rapamycin extended median mouse lifespan by roughly 9-26% depending on dose, sex, and start age, replicated across labs. Metformin alone showed no significant lifespan extension in the same testing program; a metformin-rapamycin combination performed better than metformin alone but not better than rapamycin alone.

Can you take metformin and rapamycin together?

Some prescribers combine them off-label. NIA mouse data found the combination extended lifespan more than metformin alone, though not more than rapamycin alone. There's no human safety or efficacy data on the combination, so it should only be considered with clinician monitoring of kidney function, glucose, and lipids.

What are the main risks of rapamycin at longevity doses?

Reported risks even at low, intermittent off-label doses include mouth ulcers (stomatitis), some degree of immune suppression with increased infection risk, and metabolic changes such as shifts in lipids or blood glucose. The bulk of rapamycin's documented risk data comes from continuous daily dosing in transplant patients, a different population and regimen than longevity protocols.

What are the main risks of metformin?

Common risks include GI upset (diarrhea, nausea), and a rare but serious risk of lactic acidosis, mostly in people with reduced kidney function, which is why the FDA label restricts use based on eGFR. Long-term use can also modestly reduce vitamin B12 levels.

Is rapamycin FDA-approved for anti-aging?

No. Rapamycin (sirolimus) is FDA-approved only for preventing organ transplant rejection, and related formulations (Fyarro, Hyftor) are approved for a rare soft-tissue tumor and for facial angiofibromas in tuberous sclerosis. Any use for aging, longevity, or healthy adults is entirely off-label.

Is metformin FDA-approved for anti-aging?

No. Metformin is FDA-approved only for type 2 diabetes management. Its use for aging or longevity in people without diabetes is off-label, and the trial meant to formally test it for aging, TAME, has not been completed.

How is rapamycin typically dosed differently from metformin in longevity protocols?

Metformin is usually dosed daily, similar to its diabetes use. Rapamycin, in off-label longevity protocols, is typically dosed intermittently, often weekly or every two weeks, based on mouse pharmacology suggesting pulsed dosing may spare some of the metabolic side effects seen with continuous daily dosing.

What happened to the TAME trial for metformin?

TAME was designed as a roughly 3,000-person, six-year trial testing whether metformin delays a composite of age-related diseases in people without diabetes. As of the most recent public updates from the trial's organizers, it has not secured full funding and has not been completed.

Sources

1. National Institute on Aging, Geroscience overview: The Interventions Testing Program tests compounds including rapamycin and metformin for effects on mouse lifespan, anchoring the geroscience hypothesis
2. Harrison et al., Nature 2009: Rapamycin extended median lifespan by roughly 9% in males and 13% in females when started at 600 days of age in genetically heterogeneous mice
3. Mannick et al., Science Translational Medicine 2014: A rapamycin analog (everolimus) improved influenza vaccine antibody response in elderly subjects in a Novartis-funded trial
4. AgelessRx / PEARL trial registration, ClinicalTrials.gov: The PEARL trial is studying low-dose intermittent rapamycin in healthy older adults for safety and biomarker outcomes, not mortality
5. FDA, Metformin hydrochloride prescribing information: Metformin carries a boxed warning for lactic acidosis risk and use is restricted based on kidney function (eGFR)