Short answer: rapamycin (generic name sirolimus) is an immunosuppressant approved to prevent kidney transplant rejection. Its label carries a boxed warning about infection and cancer risk from immunosuppression, and lists mouth sores (stomatitis), diarrhea, nausea, high cholesterol and swelling among its most common side effects. Longevity use is off-label and uses much lower, intermittent doses than transplant medicine; the one placebo-controlled trial in healthy adults we could read reported side effects similar to placebo over 48 weeks, but it was small and run by a company that sells the drug.
The label quotes below come from the sirolimus tablets prescribing information (a generic of Rapamune) on DailyMed, read on 1 October 2026.
What rapamycin is approved for
The sirolimus label: "Sirolimus tablets are an mTOR inhibitor immunosuppressant indicated for the prophylaxis of organ rejection in patients aged ≥13 years receiving renal transplants". There is no FDA approval for aging or longevity. A clinic prescribing it for healthspan is prescribing off-label.
The boxed warning
The sirolimus label opens with a boxed warning on immunosuppression: "Increased susceptibility to infection and the possible development of lymphoma and other malignancies may result from immunosuppression". That warning was written for continuous transplant dosing. Whether it applies with the same force at low weekly doses is exactly what longevity trials are trying to measure; it has not been settled.
Most common side effects
The sirolimus label gives two lists. The one closest to a non-transplant population is from its study in lymphangioleiomyomatosis (LAM), a rare lung disease: "Lymphangioleiomyomatosis: Most common adverse reactions (incidence ≥20%) are stomatitis, diarrhea, abdominal pain, nausea, nasopharyngitis, acne, chest pain, peripheral edema, upper respiratory tract infection, headache, dizziness, myalgia, and hypercholesterolemia".
Stomatitis means mouth sores or ulcers. It is the side effect people on low-dose rapamycin mention most often.
Other warnings on the label
The sirolimus label's warnings and precautions also include "Angioedema ( 5.5 ) • Fluid Accumulation and Impairment of Wound Healing ( 5.6 ) • Hyperlipidemia ( 5.7 ) • Decline in Renal Function ( 5.8 ) • Proteinuria ( 5.9 ) • Latent Viral Infections ( 5.10 ) • Interstitial Lung Disease/Non-Infectious Pneumonitis ( 5.11 )". In plain terms: swelling, slower wound healing, raised cholesterol and triglycerides, kidney effects, reactivated viral infections and a rare lung inflammation.
Two more points from the sirolimus label matter for healthy adults:
- Pregnancy. "Embryo-Fetal Toxicity: Can cause fetal harm. Use of highly effective contraception is recommended for females of reproductive potential during treatment and for 12 weeks after final dose of sirolimus".
- Vaccines. "Immunizations: Avoid live vaccines".
What the PEARL trial found in healthy adults
PEARL is the largest placebo-controlled human trial of low-dose rapamycin for aging that we could read in full abstract on PubMed. Its design, from that abstract: "This 48-week decentralized, double-blinded, randomized, placebo-controlled trial (NCT04488601) evaluated the long-term safety of intermittent low-dose rapamycin in a healthy, normative-aging human cohort. Participants received placebo, 5 mg or 10 mg compounded rapamycin weekly."
On safety, the PEARL abstract reports: "Adverse and serious adverse events were similar across all groups. Visceral adiposity did not change significantly". The main outcome it was designed to move did not change.
One disclosure the reader should weigh: the PEARL paper's conflict-of-interest statement reads "GH, VL, AN, MM, SM, AI, and SZ are employees and shareholders of AgelessRx." AgelessRx sells rapamycin. That does not make the result wrong, but an independent replication would carry more weight.
Questions to ask a clinician before starting
- Will you check my lipids, blood sugar, kidney function and blood counts before and during treatment?
- How will you handle mouth sores if they appear?
- Should I stop before surgery, dental work or a live vaccine?
- What evidence are you relying on for my dose, and is it from a human trial?
Who prescribes rapamycin online, at prices we verified
Of the 31 clinics we track, three publish a rapamycin price on their own pages (read October 8, 2026):
- AgelessRx: $65/month, "Billed monthly | Shipped monthly". Its page also says "Baseline and ongoing blood work included" (read October 1, 2026).
- Get Heally: a "Rapamycin Subscription" at $99, after a free consultation in which, in its words, a licensed provider "reviews your health history, explains the FDA status and risks of rapamycin, and decides whether it is appropriate for you". It adds that costs vary with the plan and dose prescribed.
- HealthRX: "Rapamycin (Sirolimus) 1 mg" at $122/month on its 12-month plan, or $152 billed monthly (read October 12, 2026).
How you get a prescription: Get Heally and HealthRX both say a licensed provider reviews each request first, and HealthRX adds that "A prescription is never guaranteed." Rapamycin is prescription-only in the U.S., and its use for longevity is off-label, as described above.
Medical disclaimer: this article summarizes the FDA label and one published trial and is not medical advice. Rapamycin suppresses the immune system; take it only under a licensed clinician who monitors you.
