Fisetin: A Clinician's Guide to Evidence, Dose & Safety

Fisetin is a plant flavonoid that has become one of the most talked-about longevity supplements on the market. The interest started with a 2018 mouse study that identified fisetin as the most potent senolytic among ten flavonoids tested [1]. A senolytic is a compound that selectively clears senescent cells — the damaged, "zombie" cells that accumulate with age and drive tissue decline.

Here is the current picture. Fisetin has substantial preclinical biology, while published human studies now span pharmacokinetics, inflammation and metabolic markers, osteoarthritis, stroke and several experimental dosing strategies. The results are mixed, the regimens are not interchangeable, and no completed human trial has shown that oral fisetin produces systemic senescent-cell clearance or a clinical longevity benefit. The most rigorous mouse lifespan study also found no lifespan extension. This guide separates what has actually been tested from what supplement marketing extrapolates.

For the endpoint-by-endpoint evidence, see our fisetin benefits review. We also maintain focused evidence pages for brain and cognition, muscle and frailty, and inflammation and joint outcomes.

Fisetin evidence at a glance: 2026

Reader question	What the evidence establishes	Full analysis
Is fisetin a senolytic?	Yes in selected laboratory and mouse models; reliable systemic senescent-cell clearance in living humans remains unproven.	Senolytic evidence
Does it improve healthspan or longevity?	Human results depend on the population and endpoint. No human longevity benefit has been established.	Benefits by outcome
What dosage works?	Human studies use different daily and intermittent schedules; none is a universally validated consumer regimen.	Human trial doses
Is absorption a problem?	A small human crossover trial found low exposure with unformulated fisetin and higher dose-adjusted exposure with a specific hydrogel preparation; clinical benefit is unproved.	Absorption and formulations
How safe is it?	Short-term trials provide limited tolerability data. Long-term high-dose and human drug-interaction risks remain insufficiently characterized.	Safety and interactions

Updated 26 September 2026. Each linked article examines the original study designs, populations, limitations and sources separately.

What is fisetin?

Also searched as: fisetine, the unaccented rendering of the French name fisétine. These names refer to the same flavonol—not different supplement ingredients. Its chemical identity is recorded in PubChem.

Fisetin is a flavonol — a subclass of the flavonoid group of plant polyphenols, with the chemical name 3,3′,4′,7-tetrahydroxyflavone. It gives the yellow colour to the smoke bush (Rhus cotinus), and it occurs naturally in strawberries, apples, persimmons, onions, grapes, and cucumbers [2].

A small historical food-intake study estimated approximately 0.4 mg/day of fisetin among 50 adult women in Japan, not a worldwide dietary average. Concentrated 100–500 mg supplement capsules deliver an entirely different exposure from ordinary food. The historical strawberry-concentration figure cannot be converted into a reliable fresh-fruit serving dose; see our food-source methods review.

Fisetin appears in supplements because of three properties: it scavenges free radicals as an antioxidant, it suppresses inflammatory signalling, and — most importantly for the longevity market — it selectively killed senescent cells in laboratory dishes in the founding 2018 screen [1].

Supplement-grade fisetin usually comes from smoke tree extract or fustic wood, not from strawberries. The extraction process concentrates the compound thousands of times above dietary levels. For the full breakdown of fisetin chemistry, sources, and the difference between dietary and supplement fisetin, see our article on what fisetin is.

For the measured food-composition data, including the variability of published strawberry estimates, see our foods high in fisetin guide. Dietary fisetin intake is not interchangeable with investigational supplement doses.

How does fisetin work in the body?

Fisetin has several proposed mechanisms. Three are well established in cells. One — senescent cell clearance — is the reason people take it as a longevity supplement, and it is also the mechanism most confused in popular coverage.

Senolytic activity: clearing senescent cells

Senescent cells are damaged cells that stop dividing but do not die. They accumulate with age and secrete inflammatory signals — the senescence-associated secretory phenotype, or SASP — that damage nearby tissue. Fisetin interferes with the survival pathways that keep senescent cells alive. In the founding 2018 paper, fisetin killed senescent human cells at 5–20 μM concentrations while leaving healthy cells intact [1], and a separate 2017 screen confirmed fisetin selectively induced apoptosis in senescent endothelial cells without harming proliferating ones [3]. Aged mice fed fisetin cleared senescent cells in fat, spleen, liver, and kidney tissue, and their median lifespan increased in that original study.

Senolytic versus senomorphic: model-specific findings

A senolytic eliminates senescent cells in a given model; a senomorphic suppresses aspects of their harmful signalling without necessarily killing them. A 2025 cell-culture study tested free and liposome-encapsulated fisetin in two doxorubicin-induced senescent lung cell lines. Both preparations reduced IL-6 and IL-8, and neither selectively killed senescent cells in that experimental model [4]. The result does not establish that liposomal delivery universally converts fisetin's activity or that one formulation should be dosed daily while another is pulsed.

Antioxidant, Nrf2 activation, and brain penetration

Fisetin scavenges free radicals directly and activates the Nrf2 pathway, the body's own antioxidant defence system [2]. It also crosses the blood-brain barrier in animal studies — unusual for a flavonoid — which is part of why it has drawn interest for cognitive ageing [5] [6].

What does the human evidence actually show in 2026?

A September 2026 narrative clinical-translation review evaluated 34 registered fisetin studies within its age-related-disease scope. Six were completed, and four had results available at the review's search cutoff. The completed studies span differing populations and endpoints, including musculoskeletal and neurological conditions; some results are favourable on selected markers while others are inconclusive or negative. Registrations alone do not establish efficacy, and the review excluded several acute-infection studies from its 34-study synthesis [34]. The protocols described below should therefore be read as individual research programmes, not a single established longevity regimen.

Preliminary conference update, not a completed full trial report: A May 2026 meeting abstract describes a randomized 10-person fisetin pilot in CVID-associated GLILD. It reports no adverse events and exploratory numerical lung-function and mental-health changes. The related trial registry still lists 20 planned participants and remains active, not recruiting; the abstract cannot establish benefit or systemic human senescent-cell clearance [35].

The completed trial: fisetin for knee osteoarthritis (2024)

The Steadman Philippon Research Institute ran a randomised, placebo-controlled trial of the pulsed fisetin protocol (roughly 20 mg/kg on two consecutive days, repeated after 28 days) in adults with knee osteoarthritis (75 recorded as actual enrollment by ClinicalTrials.gov; the 2025 OARSI abstract reports 74 randomized, 34 fisetin and 40 placebo), followed for 12 months [7] [36]. Adverse-event rates were similar to placebo in this particular trial, which does not establish long-term safety for all users. But on every efficacy measure — knee function score (WOMAC), 6-minute walk distance, a cartilage-breakdown blood marker (COMP), and inflammation (CRP) — there was no statistically significant difference from placebo at 6 or 12 months. CRP trended numerically higher in the fisetin group at 6 months, the wrong direction for benefit, though this did not reach significance. This matters because a 2017 mouse study had shown fisetin activating SIRT1 to protect cartilage in osteoarthritic joints [8] — a clean example of a promising mouse mechanism that did not translate to a measurable human benefit for this specific condition.

The frailty and senescence trials: still running

Several additional human studies are registered or underway, but their recruitment status, endpoints and dosing schedules differ:

• AFFIRM (Mayo Clinic) — fisetin 20 mg/kg/day for two consecutive days per month, testing 6-minute walk distance in older women with frailty [9].
• PROFFi (UCLA) — a 2×2 factorial design testing fisetin with and without supervised exercise, in breast cancer survivors, over 8 cycles [10].
• TROFFi (UCLA, a distinct trial from PROFFi despite the similar name and shared investigator network) — fisetin alone against placebo, 4 cycles, 88 postmenopausal breast cancer survivors with reduced walking capacity after chemotherapy [11].
• Fisetin HIGH (Copenhagen) — a pilot pharmacokinetic and senescence-biomarker trial in healthy volunteers and older patients with multimorbidity [12].
• COVID-FIS — a completed pilot safety trial in nursing home residents with COVID-19, which found the pulsed protocol safe but did not show a clear clinical benefit [13].

A September 2026 clinical-translation review identified 34 eligible registered fisetin trials across aging/frailty, metabolic disease, cancer, cardiovascular disease, neuroimmune/neurodegenerative disease and other chronic age-related conditions. Only six were completed and four had results available at the review's August 2026 registry search [34]. The field is therefore expanding, but the human efficacy evidence remains limited and heterogeneous.

Real human data at a different, lower dose

Two other kinds of human data exist outside the senolytic-dose pipeline, and both are worth knowing about precisely because they are rarely cited elsewhere.

A small open-label pilot gave ten healthy adults over 50 a much lower dose — 500 mg daily, one week per month, for six months — and measured biological age with the TruAge epigenetic test. The result was mixed: four of ten participants showed a reduction in biological age, five of ten showed an increase, and one showed no change. Telomere length did not significantly change. The authors' own conclusion: fisetin as an anti-ageing agent is not recommended until larger, controlled studies are done [15]. We are not aware of another consumer-facing fisetin article that cites this study, and we think an honest evidence page should.

Separately, a 2026 randomised controlled trial tested continuous daily fisetin (200 mg/day — much closer to what commercial capsules actually contain) combined with structured exercise in 60 obese men, reported across two companion papers from the same 60-participant cohort — one covering inflammatory markers and Maresin-1, the other covering asprosin and the lipid panel [16] [17]. Both papers were genuinely positive on metabolic and inflammatory markers: reduced IL-6 and TNF-alpha, improved insulin resistance (HOMA-IR), a 60.7% reduction in asprosin (a hormone linked to insulin resistance), and a full lipid panel improvement. This is real, positive human RCT evidence — just for a different population (obese men, not frail older adults), a different question (metabolic inflammation, not senescent cell clearance), and one trial rather than two independent replications.

The mouse lifespan result that complicates the story

The single most important caveat in this entire article: the NIA's Interventions Testing Program (ITP) — the field's most rigorous preclinical longevity test, run simultaneously across three independent US research sites in genetically heterogeneous mice — tested fisetin for lifespan extension and found no significant effect, in either sex, at either of two dosing schedules tested: continuous feeding, or a pulsed 3-days-on/11-days-off schedule closer to the human senolytic protocol [18]. Two other agents tested in the same round, astaxanthin and meclizine, did significantly extend male lifespan. Fisetin did not.

The same study went a step further than lifespan alone. It measured p16(Ink4a), a standard marker of senescent cells, directly in liver, kidney, and brain tissue from the fisetin-fed mice. Neither dosing schedule significantly lowered p16 levels compared with untreated, age-matched controls, in any of the three organs tested [18]. That is a direct biomarker test of fisetin's core premise — clearing senescent cells — and in this cohort, on this protocol, it did not show up.

This does not overturn the senolytic biology — the ITP study measured lifespan, not senescent cell clearance or physical function, which is what most other positive fisetin mouse studies measure. Murray 2025 found fisetin matched genetic senescent-cell clearance for improving frailty index and grip strength in old mice, using an intermittent dosing schedule different from the ITP's [19], and Mahoney 2023 found intermittent fisetin improved arterial function in old mice by reducing vascular senescence [20]. But "improves frailty markers in mice" and "extends lifespan in mice" are different claims, and as of the most rigorous test available, only the first has held up.

How well is fisetin absorbed?

Fisetin has poor oral bioavailability. This is the second most important thing to understand about the supplement, after the dosing gap covered below.

A 2022 crossover study in 15 healthy adults compared 1,000 mg of unformulated fisetin (approximately 982 mg actual fisetin) with 1,000 mg of a hybrid-hydrogel preparation containing only 192 mg fisetin [21]. The published Cmax and AUC comparison values were adjusted for the difference in actual fisetin content: the reported dose-adjusted Cmax was 9.97 ng/mL for unformulated fisetin and 238.2 ng/mL for FF-20, a 23.9-fold difference; dose-adjusted AUC differed by 26.9-fold. The 9.97 ng/mL figure should not be read as the unadjusted peak after 982 mg. Neither parent-fisetin plasma level establishes whether human tissues reach an effective senolytic exposure. Numerical comparisons with the 1–5 μM concentrations used in selected cell experiments are not validated human treatment thresholds. The trial was sponsored by the developer of the tested formulation, and two coauthors were employed by Life Extension, which markets FF-20 as Bio-Fisetin. Independent replication remains important. The research dose delivered 192 mg fisetin, whereas the current Bio-Fisetin retail capsule contains 8 mg; the published plasma concentrations cannot be assigned to one retail capsule without direct dose-specific data.

Rodent pharmacokinetic work tells a similar story: after intravenous dosing in rats, fisetin's parent compound declines rapidly as it is conjugated to sulfate and glucuronide metabolites, with only transient unconjugated fisetin detectable after oral dosing [22], and in mice a single intraperitoneal dose is cleared with a terminal half-life around 3.1 hours, extensively glucuronidated, with an active methoxylated metabolite called geraldol identified along the way [23].

Formulation science is actively trying to solve this. A fisetin nanoemulsion showed no bioavailability improvement after intravenous dosing but a 24-fold increase after intraperitoneal dosing in mice [24], and cyclodextrin-inclusion-complex and enzymatic-glycoside approaches are separate strategies under investigation to improve water solubility [25]. No completed human trial has established that any tested fisetin formulation reliably achieves senescent-cell clearance in people, and a universal human plasma or tissue senolytic threshold has not been validated.

What is the right dose of fisetin?

There is no single established human fisetin dose. High-dose intermittent schedules around 20 mg/kg/day remain common in senolytic-focused studies, but contemporary human research also includes 100 mg/day continuous dosing, 200 mg/day continuous dosing, a 2 mg/kg intermittent vascular protocol, and 500 mg pharmacokinetic dosing [33] [30] [31] [21]. The 200 mg/day obesity trials add another continuous-dose example [16].

That diversity matters. The roughly 20 mg/kg pulsed schedule is a research strategy, not a clinically validated "senolytic dose" for self-treatment. Human dose-ranging studies have not established an optimum regimen for senescent-cell clearance, longevity, or general health. For the full breakdown of study regimens versus commercial labels, see our dedicated dosage article and our deep dive on pulsed protocols.

How should you take fisetin?

Food effects are still being tested

Fisetin is poorly water-soluble and has low oral exposure, but the published human evidence does not yet show that simply adding dietary fat improves absorption. In the 2022 crossover pharmacokinetic study, participants took fisetin after an overnight fast and were given breakfast one hour later; that study demonstrated a formulation effect, not a fatty-meal effect [21]. The ongoing FISEKIN-1 study is specifically comparing fed and fasted fisetin exposure [32].

No time of day has been proved superior

No human trial has directly shown that morning dosing is more effective or better tolerated than evening dosing. Trial procedures vary, and the REPROGRAM protocol uses 100 mg/day with or just after an evening meal [30]. Timing should therefore be treated as a protocol or practical choice rather than an efficacy claim.

Match the regimen to the evidence you are discussing

Human studies test materially different exposure strategies, from continuous low doses to intermittent high-dose pulses. None has been established as a general-purpose longevity regimen. Our how and when to take fisetin guide separates published trial procedures from practical supplement questions.

Is fisetin safe? Side effects and drug interactions

Across the published human studies available so far, no consistent severe toxicity signal has emerged, but the safety database is still small and heterogeneous. The 12-month knee osteoarthritis trial found adverse event rates statistically identical between fisetin and placebo groups [7], and the pilot COVID-FIS trial reported no serious adverse events [13].

Long-term safety of daily fisetin at commercial capsule doses, over years rather than months, has not been formally studied in a controlled trial.

Common side effects

Human trials are too small and heterogeneous to identify the most common fisetin-specific adverse effects or their frequency. Gastrointestinal symptoms, headache, fatigue and sleep changes have been reported in some settings, but attribution and dose-response remain uncertain; significant or persistent symptoms warrant clinical review.

Drug interactions — be specific, not generic

Fisetin is metabolised through cytochrome P450 pathways and extensively glucuronidated and sulfated [22], which creates theoretical interaction risk with several medication classes rather than a single generic "ask your doctor" caveat:

• Warfarin and direct oral anticoagulants (DOACs)
• Antiplatelet drugs — aspirin, clopidogrel, ticagrelor
• Tyrosine kinase inhibitors used in cancer treatment
• Chemotherapy agents generally
• Immunosuppressants

Patients on any of these should speak with their prescriber before starting fisetin. See our full article on fisetin drug interactions.

Who should be cautious

Fisetin should not be started during pregnancy, breastfeeding, or active malignancy without specialist guidance. See our articles on fisetin in pregnancy, fisetin and blood pressure, and the full fisetin safety profile.

Human safety findings cannot be extrapolated to animals. Our veterinary fisetin review explains why no validated dog or cat dose exists and why owners should seek veterinary advice.

What else has fisetin been studied for?

Beyond the senolytic-frailty story, fisetin has a wide preclinical footprint that is worth knowing about even where human evidence does not yet exist. In skin, topical fisetin reduced UVB-induced water loss and preserved barrier proteins in a mouse model [26] — see our dedicated skin article. In hair biology, fisetin activated the TERT promoter and increased hair-growth-associated gene expression in keratinocytes [27] — see our hair growth article. In respiratory inflammation, fisetin reduced cytokine secretion in bronchial epithelial cells relevant to allergic airway disease [28]. And in cardiometabolic research, oral fisetin reduced hepatic lipid accumulation and improved cholesterol markers in a diet-induced hypercholesterolaemia mouse model via the ASGR1 pathway [29]. All of this is Tier 3–4 preclinical evidence — promising directions, not established human benefits.

How does fisetin compare to other longevity flavonoids?

Longevity supplement shelves carry several plant-derived compounds with overlapping claims. Fisetin sits alongside quercetin, spermidine, urolithin A, resveratrol, and apigenin, each targeting a different aspect of ageing biology.

Fisetin vs quercetin

Both are structurally similar flavonoids. Fisetin is more potent as a standalone senolytic in mouse studies; quercetin has more human trial data overall, mostly combined with the prescription drug dasatinib. See our fisetin vs quercetin comparison.

Fisetin vs urolithin A

Urolithin A is being studied for mitophagy and mitochondrial-related outcomes, while fisetin has senolytic activity in selected preclinical systems. Their different proposed mechanisms do not establish that combining them is safe or improves human outcomes. See our fisetin vs urolithin A comparison.

Fisetin vs spermidine, resveratrol, and apigenin

Spermidine is an autophagy inducer with more human epidemiological data than fisetin. Resveratrol is a sirtuin activator with a long, mixed human trial history. Apigenin inhibits CD38, an NAD+-consuming enzyme, which fisetin does not. See our full comparisons: fisetin vs spermidine, fisetin vs resveratrol, fisetin vs apigenin.

What we still don't know about fisetin

Six open questions matter more than any others, and we think an honest guide should lead with them rather than bury them.

Does fisetin extend lifespan? The field's most rigorous mouse test — the NIA's Interventions Testing Program — found no lifespan effect and no reduction in the p16 senescent-cell marker in liver, kidney, or brain, on either a continuous or pulsed dosing schedule [18], even though the original 2018 study that started the fisetin story did find a lifespan benefit [1]. These findings have not been reconciled.

Does fisetin work as a senolytic in humans? A completed knee-osteoarthritis trial did not demonstrate a consistent clinical or biomarker advantage across its measured outcomes [7]. Other completed studies have heterogeneous results, often with small sample sizes or different interventions. Neither those findings nor ongoing frailty trials establish systemic senescent-cell clearance or improved lifespan in humans.

What is the right human dose? No single dose has been established. High-dose intermittent schedules around 20 mg/kg are common in senolytic-focused trials, but human studies also use 100 mg/day, 200 mg/day, 2 mg/kg intermittent dosing and 500 mg pharmacokinetic doses [33] [30] [31]. None has been validated as an effective human longevity dose.

Does formulation change what fisetin actually does? Different formulations may alter exposure, but a single lung-cell experiment showing senomorphic effects from both free and liposomal fisetin cannot establish which mechanism a given retail product delivers in humans [4].

Is chronic daily dosing safe? Human research includes both daily and intermittent regimens, but available trials are too short, small or heterogeneous to establish the long-term safety of chronic supplemental fisetin in the general population.

Which conditions, if any, actually respond? Small human studies across osteoarthritis, other musculoskeletal conditions and additional populations have produced heterogeneous findings. Some investigational studies remain underway; no outcome is established as a general-purpose clinical longevity benefit.

Bottom line

Fisetin has credible senolytic and senotherapeutic biology in selected cell and animal models, but the human evidence is heterogeneous. A completed knee-osteoarthritis trial did not show an efficacy advantage, a small biological-age study was mixed, two 2026 publications from one trial in men with obesity reported changes in selected metabolic or inflammatory markers, and no completed human trial has demonstrated systemic senescent-cell clearance or a clinical longevity benefit. The Interventions Testing Program also found no lifespan extension in genetically heterogeneous mice.

Human studies now use multiple dosing strategies, including continuous low-dose regimens, lower intermittent dosing and high-dose pulses. None is established as a longevity treatment. Food effects and time-of-day effects remain unresolved, so a 20 mg/kg monthly pulse, a fatty meal or morning dosing should not be presented as a validated self-treatment formula. If you are considering supplemental fisetin—especially with prescription medicines, during pregnancy or breastfeeding, or during cancer treatment—discuss the specific product and regimen with an appropriate clinician.