Sirolimus vs NAD+: comparing the longevity evidence

Last updated 2026-07-27

What are sirolimus and NAD+ boosters, exactly?

Sirolimus is a drug. It's also called rapamycin, the same molecule, and the names are used interchangeably in research papers and in clinic. It was FDA-approved in 1999 as an immunosuppressant to prevent organ transplant rejection ^[1], and later formulations (Fyarro, Hyftor) got approved for specific rare conditions. None of its approvals cover aging or lifespan extension. Every use of sirolimus for longevity is off-label, meaning a doctor is prescribing an approved drug for a purpose the FDA never reviewed. NAD+ boosters aren't a drug. They're a supplement category: nicotinamide mononucleotide (NMN), nicotinamide riboside (NR), and related compounds that the body converts into nicotinamide adenine dinucleotide (NAD+), a coenzyme every cell needs for energy metabolism and for enzymes called sirtuins and PARPs to function. NAD+ itself can also be given intravenously, though IV NAD+ has essentially no controlled human trial base behind the longevity claims made for it. So the comparison isn't really drug-vs-drug. It's a repurposed prescription immunosuppressant with strong animal mortality data against an over-the-counter supplement with strong biomarker data and almost no animal mortality data at comparable doses. That asymmetry matters for everything that follows.

What's the actual lifespan evidence for each?

Sirolimus has the best animal aging data of any compound tested to date, full stop. The National Institute on Aging's Interventions Testing Program (ITP), running since 2004 across three labs (Jackson Lab, University of Michigan, UT Health San Antonio), found that rapamycin extended median lifespan in genetically heterogeneous mice by about 9% to 14% in males and up to roughly 21% to 26% in females at higher doses, depending on the cohort and start age ^[2]. Effects held up even when dosing started late in life, around 20 months of age (roughly equivalent to a 60-year-old human), which is unusual for a longevity intervention. NAD+ precursors have a much thinner animal lifespan record. NMN and NR studies in mice show improvements in specific measures, glucose tolerance, mitochondrial function, some age-related tissue markers, but the ITP has tested NR and did not find a lifespan extension in that program's standardized protocol ^[3]. That's a meaningful negative result from the same rigorous, multi-site testing system that validated rapamycin. It doesn't mean NAD+ precursors do nothing; it means the strongest independent test we have of 'does this extend mouse lifespan' didn't replicate for NR the way it did for rapamycin. Neither compound has a completed human lifespan trial. Nobody does; human lifespan trials would take decades and cost more than any funder has committed. That gap is the single most important thing to understand about both categories: everything sold or prescribed for longevity right now is extrapolated from animal data, mechanism, or short-term biomarker studies in people, not from evidence that either compound makes humans live longer.

Do we have any human data at all?

For sirolimus, the closest thing to human aging data is a small trial in elderly volunteers given a low-dose mTOR inhibitor (an analog related to rapamycin, everolimus) for six weeks, which improved response to influenza vaccination, a proxy for immune function, not a lifespan outcome ^[4]. There's also observational and mechanistic work in humans on skin aging and other endpoints, plus ongoing self-tracking through low-dose intermittent protocols that clinicians report on informally, but no completed randomized controlled trial has measured mortality, disease-free survival, or a validated aging clock as a primary endpoint over years. For NAD+ precursors, there are more human trials, but they're short and biomarker-focused. Placebo-controlled studies of NMN and NR in humans, typically 8 to 12 weeks, consistently raise blood NAD+ levels and show some improvements in markers like blood pressure or muscle-related measures in specific populations ^[5]. None of these trials run long enough or are powered to detect anything about lifespan or even slowed functional decline over years. A few have shown null results on the specific outcome they were testing for, which happens often enough in supplement trials that it's worth taking claims with real caution. So human data volume favors NAD+ precursors (more trials, shorter, safety-focused), while human data on sirolimus is sparser but more mechanistically tied to the pathway (mTOR) that the strongest animal aging data implicates.

How do the mechanisms differ?

Sirolimus inhibits mTOR (mechanistic target of rapamycin), a nutrient-sensing pathway that, when chronically overactive, drives cell growth and protein synthesis at the expense of maintenance processes like autophagy (cellular cleanup). Dialing mTOR down, especially mTORC1, is one of the most reproducible ways to extend lifespan across yeast, worms, flies, and mice, which is part of why the ITP results are taken seriously; the biology isn't a one-off, it's consistent across species that diverged hundreds of millions of years ago ^[2]. NAD+ precursors work upstream of different targets. NAD+ is a cofactor for sirtuins (proteins linked to stress resistance and metabolic regulation) and for PARPs (DNA repair enzymes) and CD38 (an enzyme that consumes NAD+). NAD+ levels fall with age in many tissues, so the logic is that restoring them restores the function of enzymes that depend on them. It's a plausible mechanism, but plausible mechanism is not the same as a validated lifespan effect, and the mTOR pathway has a much longer track record of translating from mechanism into measured lifespan extension in mammals.

How do the real-world risks compare?

Sirolimus carries risks that come from being an actual immunosuppressant. At transplant doses, it meaningfully increases infection risk and is linked to other complications tracked in FDA prescribing information . At the low, intermittent doses used off-label for longevity (often once-weekly rather than daily), the risk profile is different and likely smaller, but there is no long-term safety trial in healthy people to quantify it precisely. Reported issues at these lower doses include mouth ulcers (a common and sometimes limiting side effect), elevated LDL cholesterol and triglycerides, and mild increases in blood glucose in some users. These are real, documented pharmacological effects of mTOR inhibition, not rare idiosyncratic reactions. NAD+ precursors have a much milder reported side effect profile in the trials that exist: flushing (more with IV NAD+ or high oral doses), mild GI upset, headache. No signal for immunosuppression or metabolic disruption in the human trials so far. But 'milder in short trials' isn't the same as 'proven safe long-term'; nobody has run a multi-year safety trial either, and the FDA sent a notice in 2022 stating NMN doesn't meet the definition of a lawful dietary supplement ingredient, which changed how some NMN products are marketed in the US (NR is unaffected by that specific determination). If you're comparing 'what could go wrong,' sirolimus has a known, biologically serious risk (immune suppression) that requires monitoring; NAD+ precursors have a milder but far less studied risk profile and an unsettled regulatory status for at least one common form.

What does each cost, and how is each actually taken?

Sirolimus is a prescription drug. It requires a doctor, typically bloodwork before starting (lipid panel, kidney function, sometimes a CBC) and periodic monitoring after. Off-label longevity protocols are usually intermittent, for example once weekly rather than the daily dosing used in transplant medicine, based on the reasoning that pulsed dosing may capture the autophagy benefit while limiting continuous immune suppression, though this specific dosing pattern hasn't been tested in a completed human lifespan or healthspan trial either. Costs vary by pharmacy, dose, and whether it's compounded; a provider-reviewed telehealth path (like the one Sirolimus Rx connects patients through) typically involves a consult fee plus the prescription cost, filled through a licensed pharmacy partner, rather than a flat drugstore price. Anyone starting should read a real dosing reference first (our Sirolimus Rx dosage guide covers the common off-label ranges) and use a dosage calculator rather than guess. NAD+ precursors are sold over the counter, no prescription or bloodwork required, which is a big part of their appeal. Oral NMN and NR capsules run from roughly $30 to $100+ a month depending on brand and dose. IV NAD+ infusions cost far more, often $200 to $600+ per session at longevity or wellness clinics, and require repeat sessions since the effect isn't durable. The accessibility gap between 'go buy it today' and 'get bloodwork and a prescription' is real and explains a lot of NAD+'s popularity even though its lifespan evidence is thinner.

Sirolimus vs NAD+: the side-by-side

Can you take sirolimus and NAD+ together?

People do combine them, reasoning that mTOR inhibition and NAD+ restoration hit different pathways and might be complementary. There's no published human trial testing the combination for safety or effect, so anyone doing this is relying on mechanism and personal risk tolerance, not evidence. The mechanistic case isn't crazy: mTOR and NAD+-dependent sirtuins interact in cell biology in ways researchers have mapped in animal models, but 'interact in animal models' is a long way from 'safe and beneficial to combine in a 55-year-old taking both off-label.' If someone is going to combine them anyway, the practical concern is monitoring, not interaction toxicity. Sirolimus requires bloodwork; NAD+ precursors generally don't shift the labs a doctor is already watching. The reasonable approach is treating sirolimus as the piece that needs medical oversight and NAD+ supplementation as the lower-stakes addition on top, not the other way around.

How is sirolimus dosed for longevity, and does that change the comparison?

Off-label longevity protocols for sirolimus are almost always intermittent, commonly a single weekly dose in the range discussed in published human safety and immune-function work, rather than the continuous daily dosing used in transplant medicine ^[4]. The idea, based on pharmacokinetics and animal dosing patterns from the ITP, is that spacing doses out may let mTORC1 inhibition happen in pulses, potentially preserving more of the immune benefit while still hitting the autophagy-related mechanism implicated in the mouse lifespan data. This is a reasonable, mechanism-based hypothesis. It is not a proven human protocol. Because the drug has a long half-life and reconstitution and injection aren't relevant to oral sirolimus tablets or capsules (some formulations are oral solution, requiring careful measurement rather than reconstitution), getting the dose and interval right matters more than with a forgiving supplement like NAD+, where missing a day changes little. This is exactly the situation where working from a real reference source, not guesswork, matters: see our guides on Sirolimus Rx dosage, cycle length, and the dosage calculator for how these intermittent schedules are typically structured.

Which one actually has better longevity evidence right now?

On animal data, it isn't close: sirolimus has one of the most replicated mammalian lifespan findings in the field, run independently at three labs by the NIA's own testing program, with effect sizes in the 9% to 26% range for median lifespan depending on sex and dose ^[2]. NAD+ precursors have real, measurable effects on NAD+ levels and some biomarkers in short human trials, but the equivalent large-scale mouse lifespan test (ITP testing NR) did not find a lifespan benefit ^[3]. On human evidence, both are in the same boat: no completed trial has shown either compound extends human lifespan or slows a validated marker of human aging over years. Sirolimus has a small human trial suggesting an immune-function benefit in older adults ^[4]; NAD+ precursors have more human trials but shorter ones, focused on biomarkers rather than aging outcomes. So the honest answer is: sirolimus has the stronger animal case by a wide margin, and neither has the human case yet. Anyone telling you otherwise, in either direction, is overstating what the data shows.

What would change this comparison in the next few years?

A completed randomized trial in humans measuring a hard outcome, mortality, major disease incidence, or a well-validated biological age clock over multiple years, for either compound would change everything. Several groups are working toward this for rapamycin (dog aging studies like the Dog Aging Project's TRIAD trial are already underway and will report before any human lifespan trial could) , and dog data, while not human data, is a faster and biologically closer proxy than mouse data alone since dogs share our environment and get many of the same age-related diseases. For NAD+ precursors, a positive, well-powered mouse lifespan result from an independent testing body like the ITP would meaningfully strengthen the case; right now the closest attempt (NR) didn't replicate a lifespan effect ^[3]. Until one of these things happens for either compound, both remain 'promising mechanism, real animal or biomarker data, no proof it extends human life' categories, just at different points on that spectrum.

Frequently asked questions

Is rapamycin the same thing as sirolimus?

Yes. Rapamycin is the original name for the compound discovered on Easter Island in the 1970s; sirolimus is its generic drug name once the FDA approved it in 1999 as an immunosuppressant ^[1]. They're the same molecule and the terms are used interchangeably in both research papers and prescriptions.

Does NAD+ actually extend lifespan in animals?

Not clearly. NAD+ precursors improve specific biomarkers (mitochondrial function, glucose tolerance) in mouse studies, but when the NIA's Interventions Testing Program tested nicotinamide riboside using its standardized multi-lab protocol, it did not find a lifespan extension ^[3], unlike rapamycin which showed consistent gains across the same program ^[2].

Which is safer, sirolimus or NAD+ supplements?

NAD+ precursors have a milder short-term side effect profile (flushing, mild GI upset) in the human trials that exist. Sirolimus carries known immunosuppression risk plus mouth ulcers, elevated lipids, and glucose changes, especially at higher or continuous doses ^[6]. Neither has long-term human safety data at longevity doses, so 'safer' means safer in the short term studied, not proven safe over years.

Can I take sirolimus and NAD+ supplements at the same time?

People do, but no published human trial has tested the combination for safety or added benefit. The mechanisms are different (mTOR inhibition vs. NAD+ cofactor restoration) so a real interaction risk isn't obvious, but that's an educated guess based on mechanism, not trial evidence.

Why is sirolimus prescription-only but NAD+ is sold over the counter?

Sirolimus is an FDA-approved drug with a defined risk profile requiring monitoring, so it's legally prescription-only. NAD+ precursors are marketed as dietary supplements, a much lighter regulatory category, though the FDA stated in 2022 that NMN doesn't meet the definition of a lawful supplement ingredient ^[7], which has affected some NMN product marketing.

Has anyone actually proven sirolimus extends human lifespan?

No. There is no completed human lifespan trial for sirolimus. The strongest evidence is from the NIA's Interventions Testing Program in mice, showing 9% to 26% median lifespan extension depending on sex and dose ^[2], plus one small human trial showing improved immune response to flu vaccination in older adults ^[4], which is not a lifespan outcome.

What's the difference between oral NAD+ precursors and IV NAD+?

Oral NMN and NR are capsules the body converts into NAD+ over hours; they're cheap ($30-$100+/month) and have short human trials backing biomarker changes. IV NAD+ is infused directly, costs far more per session ($200-$600+), and has even less controlled trial evidence behind the longevity claims made for it.

What dose of sirolimus do people use for longevity?

Off-label protocols typically use a low, intermittent dose, often weekly rather than daily, distinct from the continuous daily transplant regimen. Specific amounts vary by body weight, bloodwork, and prescriber judgment; see a real dosing reference and calculator rather than copying an online forum's number.

Do mouth ulcers from sirolimus go away?

For many people they're dose-dependent and improve or resolve when the dose is lowered or the schedule is spaced out further, since mouth ulcers are a well-documented mTOR-inhibitor class effect. They can be significant enough that some people stop or adjust their protocol because of them; this is worth discussing with the prescribing clinician rather than pushing through.

Is NMN legal to sell as a supplement in the US?

It's complicated. In 2022 the FDA stated that NMN doesn't meet the definition of a lawful dietary supplement ingredient because it was first studied as a drug, which has led some retailers to pull or reformulate NMN products ^[7]. Enforcement has been inconsistent, and NR (a related precursor) isn't affected by that specific determination.

Which has more human clinical trials, sirolimus or NAD+ precursors?

NAD+ precursors have more completed human trials, but they're short, typically 8 to 12 weeks, and focused on biomarkers like blood NAD+ levels rather than aging outcomes ^[5]. Sirolimus has fewer human trials in healthy or older populations, but the ones that exist tie more directly to a mechanism (immune function) linked to its animal lifespan data ^[4].

What is the NIA Interventions Testing Program and why does it matter here?

It's a National Institute on Aging program running since 2004 that tests candidate longevity compounds in genetically diverse mice across three independent labs (Jackson Lab, University of Michigan, UT Health San Antonio) to make sure results replicate. It found rapamycin extends lifespan consistently but did not find a lifespan benefit for nicotinamide riboside ^[2][3].

Sources

1. FDA, Rapamune (sirolimus) approval history: Sirolimus was FDA-approved in 1999 as an immunosuppressant to prevent organ transplant rejection
2. National Institute on Aging, Interventions Testing Program: Rapamycin extends median lifespan in genetically heterogeneous mice across three independent labs, with effect sizes varying by sex and dose
3. National Institute on Aging, Interventions Testing Program results: The ITP tested nicotinamide riboside and did not find a lifespan extension effect
4. Mannick JB, et al., Science Translational Medicine (2014): Low-dose mTOR inhibition improved immune response to influenza vaccination in elderly volunteers over six weeks
5. Irie J, et al., Endocrine Journal (2020), NR/NMN human trial data: Short-term (8-12 week) placebo-controlled human trials of NAD+ precursors raise blood NAD+ levels and show some biomarker changes