Fisetin dosage: the “hit-and-run” trial protocol vs the supplement bottle

There isn’t one fisetin “dose” — there are two, and they barely resemble each other. One is the intermittent, high-dose senolytic protocol being tested in human trials. The other is the modest daily capsule sold in supplement bottles. Confusing the two is the most common mistake people make with fisetin, so this page keeps them apart. For what fisetin actually does at those doses — and why the human efficacy case is still unproven — read the companion fisetin evidence monograph first.

The dose the trials use: a “hit-and-run” burst

The senolytic idea is not to keep a drug in the body continuously, but to hit senescent cells hard for a day or two, clear them, and then stop — a pattern the original research literally called a “hit-and-run” mechanism.^[1] The human trials built their dosing around that idea. In the Mayo Clinic AFFIRM pilot in older women with frailty, the schedule was fisetin 20 mg/kg/day, taken orally for 2 consecutive days, repeated over consecutive months.^[2] The same high, short-burst pattern recurs across the other trials: a sepsis trial gives a single 20 mg/kg oral dose or two 20 mg/kg doses one day apart,^[3] and a trial in breast-cancer survivors gives 20 mg/kg/day on days 1–3 of a 14-day cycle for four cycles.^[4] The doses are large; the exposure is brief and infrequent.

Where the strategy comes from: mice

This isn’t a dosing scheme someone invented for a supplement label — it is lifted from the animal work. In the landmark study, acute or intermittent fisetin reduced senescence markers across tissues and, given to old mice late in life, extended median and maximum lifespan, consistent with that hit-and-run clearance rather than continuous suppression.^[1] A later independent study used an explicitly on-off schedule (one week on, two weeks off, one week on) and improved frailty and grip strength in old mice while doing nothing in young ones.^[6] The intermittent design is the point, not an afterthought. It also mirrors the dasatinib-plus-quercetin senolytic protocols that pioneered this “pulse” approach.

The gap between the trial protocol and the bottle

Put actual numbers on it. Twenty milligrams per kilogram in a 70 kg adult is about 1400 mg in a single day — and the trial schedule delivers that on two days back to back.^[2] The everyday supplement dose is 100 to 500 mg per day. So a single trial “burst” day is roughly three to fourteen times a daily OTC capsule, and the two regimens differ not just in size but in shape: a rare spike versus a constant trickle. Taking 100 mg of fisetin every day is not a smaller version of the trial protocol — it is a different intervention that no senolytic trial has tested.

Bioavailability: the label is not the bloodstream

Part of why trial doses are so high is that fisetin is poorly absorbed. The only published human pharmacokinetic study gave 15 healthy volunteers a 1000 mg dose of ordinary (unformulated) fisetin and measured a peak blood level of only about 10 ng/mL; an encapsulated formulation reached roughly 27× the total exposure of the same amount of plain fisetin.^[5] The practical consequence is blunt: the number of milligrams on a supplement facts panel tells you very little about how much actually reaches your tissues, because absorption depends heavily on the formulation. It also means two “500 mg” products can behave nothing alike.

The honest bottom line

If you strip fisetin dosing to its essentials: the senolytic strategy under study is an intermittent ~20 mg/kg/day burst for two days, repeated monthly — a hit-and-run pulse drawn from mouse studies, not the low daily capsule most people buy.^[1][2] The two regimens aren’t interchangeable, poor absorption muddies every dose figure, and the trials that would tell us whether the burst schedule actually helps humans haven’t reported results yet.^[4][5] Treat the trial dose as a research protocol to watch, not a plan to run. For related intermittent-dosing longevity compounds that have reached human study, see spermidine.