Medical Disclaimer: This content is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider before making any health-related decisions. If you are experiencing a medical emergency, call your local emergency services immediately.
What This Page Explains
This page summarizes what is currently known about fisetin safety from published clinical data, preclinical toxicology studies, and dietary exposure history. While fisetin has a long history of consumption through foods, its safety profile at supplemental doses (100–2000 mg) is less well-characterized.
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Detailed Evidence
The most relevant human safety data comes from the COVFIS trial series, which used fisetin at approximately 20 mg/kg/day (roughly 1400 mg for a 70 kg adult) administered over 2 consecutive days. The treatment was generally well-tolerated. The most common adverse events were mild gastrointestinal symptoms: nausea, loose stools, and abdominal discomfort.
Evidence Hierarchy
Systematic Reviews & Meta-Analyses
Multiple high-quality trials combined
Randomized Controlled Trials (RCTs)
Gold standard for treatment efficacy
Observational Studies
Can show associations, not causation
Case Reports & Expert Opinion
Hypothesis-generating only
Preclinical (Lab/Animal) Studies
Should NOT be extrapolated to humans
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Study Quality Indicators
Higher Quality Indicators
- Large sample size (hundreds to thousands)
- Randomized and blinded design
- Placebo-controlled comparison
- Published in peer-reviewed journals
- Replicated in multiple studies
- Registered trial protocol before starting
Lower Quality Indicators
- Small sample size (under 100)
- No control group or blinding
- Manufacturer-funded with conflicts
- Only animal/cell studies
- Never replicated
- Published in predatory journals
Important Limitations
- • Supplement research often has methodological limitations
- • Results from one study may not generalize to all people
- • Marketing claims often exceed what research supports
- • Absence of evidence is not evidence of absence
- • Individual response to supplements varies widely
Quick Answers
Is fisetin safe?
Fisetin has been consumed through foods for millennia. In clinical trials, doses of 20 mg/kg/day for 2 consecutive days have been used without serious adverse events. Mild GI symptoms are the most commonly reported side effects.
What are fisetin side effects?
The most common adverse events are mild gastrointestinal symptoms: nausea, loose stools, and abdominal discomfort. These typically resolve without intervention.
Does fisetin interact with medications?
Fisetin may interact with medications metabolized by CYP3A4 and CYP1A2 enzymes based on in vitro studies. Clinical drug interaction studies have not been published. Caution is advised for individuals taking prescription medications.
Can fisetin cause liver damage?
Preclinical toxicology studies have not identified target organ toxicity at relevant doses. No liver damage has been reported in published human trials, though comprehensive safety studies have not been completed.
Is fisetin safe during pregnancy?
No human safety data exists for fisetin supplementation during pregnancy or breastfeeding. Use is not recommended in these populations.
Can you take too much fisetin?
Acute toxicity studies in rodents indicate an LD50 well above doses used in human trials. However, long-term safety of high-dose supplementation has not been characterized in humans.
Does fisetin thin the blood?
Some flavonoids have been shown to have anti-platelet effects. While fisetin-specific anticoagulant interactions have not been documented in humans, individuals on blood thinners should exercise caution.
Is fisetin safe for older adults?
The COVFIS trial demonstrated safety and feasibility of fisetin in frail elderly nursing facility residents. The treatment was generally well-tolerated in this population.
How long has fisetin been studied in humans?
Total human safety exposure in published controlled trials involves fewer than 500 participants. The longest published human exposure duration is approximately 2 weeks.
Should I tell my doctor about fisetin?
Yes. Always inform your healthcare provider about all supplements you take, including fisetin. This is especially important if you take prescription medications or have underlying health conditions.
Key Research Facts
In the COVFIS trial, fisetin at ~20 mg/kg/day for 2-day courses was administered to frail elderly residents without serious adverse events attributed to the intervention.
Moderate EvidenceVerdoorn et al., JAGS — doi:10.1111/jgs.17416
The most common adverse events reported with fisetin were mild gastrointestinal symptoms: nausea, loose stools, and abdominal discomfort.
Moderate EvidenceVerdoorn et al., JAGS — doi:10.1111/jgs.17416
Fisetin may interact with CYP3A4 and CYP1A2 cytochrome P450 enzymes based on in vitro inhibition studies, but no clinical drug interaction data exists.
Moderate EvidenceGrynkiewicz & Demchuk, Frontiers in Chemistry — doi:10.3389/fchem.2019.00159
Fisetin has been consumed as part of the human diet through fruits and vegetables for millennia, with typical intake of 0.2–1.4 mg/day.
Strong EvidenceKhan et al., Antioxidants & Redox Signaling — doi:10.1089/ars.2012.4901
Total human safety exposure in published controlled trials involves fewer than 500 participants as of early 2026.
Strong EvidenceLiterature review — PubMed/ClinicalTrials.gov search
No safety data exists for fisetin use during pregnancy, lactation, or in pediatric populations.
Strong EvidenceSafety review — Literature gap analysis
Long-term effects of repeated senolytic dosing cycles with fisetin have not been characterized in any human study.
Strong EvidenceLiterature review — PubMed search, 2026
Citations & External Resources
ClinicalTrials.gov — Search: Fisetin
EBioMedicine — Yousefzadeh et al. 2018 (Landmark Senolytic Study)
JAGS — Verdoorn et al. 2021 (COVFIS Trial)
FDA — Dietary Supplement Guidance
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Related Reading
Fisetin: Overview, Evidence & Safety
Fisetin Dosage: Research Summary
Fisetin Benefits: What the Evidence Shows
References (3)
Written by
ReCellence™ Editorial Team
Health Content Specialists
Medically reviewed by
Medical Review Board
MD, PhD
Last updated: March 8, 2026
Last medical review: March 8, 2026