Most people taking rapamycin for longevity take 6 mg once per week, though doses in practice range from 2 mg to 8 mg weekly for commercial formulations and up to 15 mg for compounded versions. This is a fundamentally different approach from its FDA-approved use in organ transplant patients, who take 2 to 5 mg every single day to suppress their immune systems. The weekly, low-dose strategy aims to briefly inhibit a cellular growth pathway called mTOR without the sustained immune suppression that comes with daily use.
Rapamycin is not approved for longevity. Everything below reflects off-label practices drawn from clinical research, pharmacokinetic data, and real-world cohort studies. If you’re considering it, you’ll need a prescribing physician willing to monitor you.
Why Once a Week, Not Once a Day
Rapamycin has a long half-life in the body, roughly 60 hours in healthy adults. That means after a single dose, it takes about two and a half days for your blood levels to drop by half. A weekly dose creates a sharp peak followed by a gradual decline to near-zero levels before the next dose. This pulsed pattern is the core idea behind longevity dosing: you get a brief window of mTOR inhibition (which triggers beneficial cellular maintenance processes like autophagy) followed by several days where the pathway recovers fully.
Daily dosing, by contrast, keeps blood levels continuously elevated. That’s necessary for transplant patients who need round-the-clock immune suppression, but it also drives most of rapamycin’s serious side effects, including glucose intolerance, elevated blood lipids, and immune vulnerability. Animal research published in Molecular Metabolism found that intermittent rapamycin treatment extended lifespan to the same degree as continuous treatment in male mice, while partially avoiding the glucose intolerance caused by chronic dosing.
Common Dosing Ranges
A 2025 study in GeroScience analyzing real-world longevity cohorts found that 6 mg per week was by far the most commonly prescribed dose. The study included people taking commercial rapamycin (brand name Rapamune or generic sirolimus) at doses of 2, 3, 6, or 8 mg, along with others using compounded formulations at 5, 10, or 15 mg. Blood levels 24 hours after dosing varied significantly between individuals even at the same dose, which is one reason monitoring matters.
Many physicians start patients at 1 to 3 mg weekly and increase gradually based on bloodwork and side effects. There’s no consensus protocol, but the general principle is to use the lowest effective dose and adjust based on your body’s response.
Food, Timing, and Consistency
How you take rapamycin relative to food significantly affects how much your body absorbs. A high-fat meal increases total absorption of the oral solution by about 35% compared to taking it on an empty stomach. For the tablet form, a high-fat meal increases peak blood concentration by 65% and total exposure by 23%.
The FDA label for Rapamune emphasizes one rule above all others: take it consistently. Pick either always with food or always without food, and stick with that pattern every time. Switching between fed and fasted states from week to week creates unpredictable swings in how much drug actually reaches your bloodstream. If you’re taking it with food, a meal containing some fat will increase absorption. If you prefer fasting, take it at least an hour before or two hours after eating.
Take the tablet whole with water. The oral solution form has its own handling requirements, but most longevity users are prescribed tablets.
Grapefruit Juice: A Powerful and Risky Amplifier
Grapefruit juice dramatically increases rapamycin blood levels by blocking intestinal enzymes (CYP3A4) that normally break down the drug before it reaches your bloodstream. In a Phase 1 cancer study, grapefruit juice increased rapamycin exposure by approximately 350%. Some longevity practitioners have experimented with small amounts of grapefruit juice to boost the effective dose while using fewer milligrams of the drug, reducing cost. This is genuinely risky. A 350% increase in drug exposure turns a 6 mg dose into the rough equivalent of 21 mg or more, and the effect varies unpredictably between individuals. Unless your physician is specifically managing this interaction with blood level testing, avoid grapefruit and grapefruit juice entirely.
Cycling On and Off
Some physicians prescribe rapamycin in cycles, for example eight weeks on followed by four weeks off. Others recommend continuous weekly dosing without breaks. There isn’t strong human evidence favoring one approach over the other for longevity purposes. The animal data suggests intermittent dosing preserves most of the lifespan benefit while reducing metabolic side effects, but “intermittent” in those studies meant alternating weeks of treatment with weeks off, not the multi-week cycles some clinicians use.
The rationale for cycling is practical: it gives the body periodic breaks to normalize blood lipids, blood sugar, and immune function. If your lab values stay stable on continuous weekly dosing, there may be less reason to cycle. If you notice side effects creeping in, a break can help reset things.
Side Effects to Watch For
The most common side effect at longevity doses is mouth sores, which appear as small, painful ulcers resembling canker sores. In transplant patients taking daily rapamycin, these occur in up to 20% of people. At lower weekly doses the rate is likely lower, but they remain the side effect you’re most likely to encounter.
These sores respond well to topical corticosteroid treatments. A retrospective analysis found that 87% of patients with rapamycin-related mouth ulcers improved with corticosteroid therapy, either applied directly to the sore or used as a swish-and-spit rinse. Prevention helps too: use a soft toothbrush, avoid alcohol-based mouthwashes and toothpastes containing sodium lauryl sulfate, and steer clear of acidic, spicy, or crunchy foods in the days following your dose. If sores appear, report them early rather than waiting for them to worsen.
Other potential side effects include elevated cholesterol and triglycerides, mildly impaired glucose tolerance, and increased susceptibility to minor infections. These are more common with higher doses and continuous use, which is why bloodwork matters.
What to Monitor With Blood Tests
Rapamycin has a narrow therapeutic window. In transplant medicine, the target blood concentration is 5 to 15 ng/mL, with levels above 15 ng/mL linked to low platelet counts, low white blood cell counts, and high triglycerides. Longevity users aren’t aiming for that sustained range since weekly dosing means levels peak and then fall well below it. But checking a trough level (blood drawn just before your next weekly dose) can confirm the drug is clearing your system appropriately between doses.
Beyond rapamycin levels themselves, most prescribing physicians monitor a standard panel that includes fasting glucose or HbA1c (to catch glucose intolerance early), a full lipid panel (total cholesterol, LDL, HDL, triglycerides), and a complete blood count to track white blood cells and platelets. A reasonable schedule is bloodwork every four to six weeks when starting or changing doses, then every two to three months once levels are stable. Liver and kidney function panels are also typically included since rapamycin is metabolized by the liver.
Commercial vs. Compounded Formulations
Rapamycin is available as brand-name Rapamune, generic sirolimus tablets, and compounded formulations from specialty pharmacies. The 2025 GeroScience study found notable differences in blood levels between commercial and compounded versions, even at similar doses. Commercial tablets are manufactured under strict FDA oversight with established bioavailability data. Compounded versions can vary in absorption depending on the pharmacy’s formulation process. If you switch between formulations, blood level testing becomes especially important to make sure you’re still in the range your physician intended.
Cost is often the reason people turn to compounding pharmacies. Brand-name Rapamune and even generic sirolimus can be expensive without insurance coverage for off-label use. If you go the compounded route, choose a pharmacy that provides certificates of analysis and has a strong reputation in the longevity medicine community.