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📰Read the full Quercetin evidence review on GMJ News →Complete clinical article, references and updates on news.gmj.ge. This page is the structured safety summary.⚠ Patient asking about senolytics — D+Q is research-stage; dasatinib is Rx chemo drug [3]
⚠ Low bioavailability (~2%) — phytosome form is 20× better absorbed [2]
⚠ Patient on cyclosporine + quercetin — CYP3A4/P-gp interaction [2]
ℹ️ Not obtained from food. A plant flavonoid from fruit and vegetables rather than a nutrient with a daily dietary target.
🔬 Lab interpreter
Recommended test
No routine monitoring
No routine monitoring
Reference range / target
N/A
N/A
Clinical assessment of target condition [2].
Full lab monitoring ↓⚕ For professionals — confirm ranges against your local laboratory.
Clinical verdict
Quercetin is the most abundant dietary flavonoid with antioxidant, anti-inflammatory, mast cell-stabilizing, and emerging senolytic properties. The D+Q (dasatinib + quercetin) senolytic regimen is the frontier of aging research but NOT yet approved. Bioavailability is only ~2% — use phytosome or isoquercetin forms. Natural antihistamine for allergies. COVID claims were overhyped [1] [2] [3].
1 How much do I need?
👤 Adults: Specific dosage data under clinical review
👴 Elderly: Specific dosage data under clinical review
🤰 Pregnancy: See guidance
Safe at dietary levels. Supplemental doses not studied in pregnancy [1].
👦 Pediatric: See guidance
Safe at dietary levels. No supplementation data in children [1].
🏃 Athletes: Standard dose
⚖️ Obesity: Standard dose
Fat-soluble compounds may require dose adjustment in obesity.
🩺 Renal: Consult specialist
Dose adjustment may be needed in renal impairment.
🌱 Vegan: Standard dose
How to take
🍽 Timing: With meals containing fat [2].
💊 With food: Fat enhances absorption. Vitamin C and bromelain may further improve bioavailability [2].
🚫 Avoid: High doses with cyclosporine [2].
2 Which form?
| Form | Bioavailability | Vegan | Cost |
|---|---|---|---|
| ['Quercetin dihydrate', 'common', 'Standard form. Low bioavailability (~2%). Take with fat and vitamin C [2].'] | Standard | Check label | |
| ['Quercetin phytosome (Quercefit)', 'preferred', 'Phospholipid complex with 20× improved absorption vs standard quercetin [2].'] | Standard | Check label | |
| ['Isoquercetin (quercetin-3-glucoside)', '', 'Glycosylated form with better water solubility and ~5× improved absorption [2].'] | Standard | Check label |
3 Common questions
What is a senolytic? ▼
Senolytics selectively destroy senescent ('zombie') cells that accumulate with aging and secrete inflammatory factors (SASP). Quercetin + dasatinib (D+Q) is the most studied senolytic combination. Dasatinib is a prescription chemotherapy drug — the combination is NOT available OTC [3].
Does quercetin help allergies? ▼
Quercetin stabilizes mast cells and inhibits histamine release — it is a natural antihistamine [1]. Some clinical evidence supports use for allergic rhinitis. However, the effect is modest compared to pharmaceutical antihistamines, and poor bioavailability limits oral efficacy.
Can food provide enough quercetin? ▼
Did quercetin work for COVID? ▼
It was theorized as a zinc ionophore (helping zinc enter cells to inhibit viral replication). Clinical trials were mixed and inconclusive. It is NOT a proven COVID treatment or prevention [2].
4 Clinical evidence
Strong
Potent antioxidant and NF-κB inhibitor in vitro and animal studies [1]. Mast cell stabilization: inhibits histamine release from mast cells — natural antihistamine mechanism [1]. Senolytic activity: quercetin + dasatinib selectively eliminates senescent cells in animal models and early human trials [3]. HIGH
Moderate
Senolytic human data: D+Q (dasatinib 100 mg + quercetin 1,000 mg × 3 days) reduced senescent cell markers in diabetic kidney disease patients (pilot, n=9) and IPF patients [3]. Blood pressure: meta-analysis of 7 RCTs showed ~3 mmHg SBP reduction with ≥500 mg/day [2]. Allergy/histamine: some evidence for reducing allergic rhinitis symptoms [1]. Exercise performance: modest improvements in VO2max in some trials [2]. MODERATE
Insufficient
5 Safety, toxicity & adverse events
Relative
⚠ Concurrent cyclosporine — quercetin increases cyclosporine bioavailability
⚠ Concurrent fluoroquinolones — quercetin competes for DNA gyrase binding
⚠ Concurrent digoxin — may increase digoxin levels via P-gp inhibition
⚠ Thyroid — high doses may inhibit thyroid peroxidase (TPO)
🚩 Red flags
● Patient buying quercetin for COVID prevention — evidence was inconclusive [2]
● Patient self-administering dasatinib + quercetin 'senolytic protocol' without medical supervision — dasatinib is a chemo drug with serious side effects [3]
6 Interactions
Drug interactions
Cyclosporine Major
Mechanism: Quercetin inhibits CYP3A4 and P-glycoprotein, potentially increasing cyclosporine levels. [2]
Effect: Elevated cyclosporine levels; nephrotoxicity risk. [2]
Action: Avoid or monitor cyclosporine levels [2].
Fluoroquinolones Moderate
Mechanism: Quercetin may compete for bacterial DNA gyrase binding. [2]
Effect: Theoretical reduced antibiotic efficacy. [2]
Action: Avoid concurrent use during fluoroquinolone treatment [2].
Supplement synergies
Vitamin C · 500–1,000 mg/day
Synergistic antioxidant. Vitamin C regenerates oxidized quercetin and enhances absorption [1].
Synergistic antioxidant. Vitamin C regenerates oxidized quercetin and enhances absorption [1].
Bromelain · 100–500 mg bromelain
Proteolytic enzyme that enhances quercetin absorption. Often co-formulated [2].
Proteolytic enzyme that enhances quercetin absorption. Often co-formulated [2].
Zinc · 15–30 mg zinc
Quercetin may function as a zinc ionophore, facilitating zinc entry into cells [2].
Quercetin may function as a zinc ionophore, facilitating zinc entry into cells [2].
7 Regulatory
United States (FDA): GRAS as food ingredient. Dietary supplement. No drug claims [1].
European Union (EFSA): Available as food supplement. No authorized health claims for quercetin specifically [1].
South Korea: Available as dietary supplement.
Senolytic use: Quercetin + dasatinib is in clinical trials (Mayo Clinic, others). NOT an approved therapy [3].
8 US supplement products
430
on-market products containing Quercetin (NIH DSLD)
Brands carrying Quercetin (172)
Click a brand to see its Quercetin products.
9 Frequently paired with
10 Cite this page
Vancouver: Pkhakadze G. Quercetin — safety profile [Internet]. Tbilisi: PHIG; 2026 [cited 2026 Oct 16]. Available from: https://supplement.ge/ingredients/quercetin/
APA 7th: Pkhakadze, G. (2026). Quercetin — Safety profile. Public Health Institute of Georgia. https://supplement.ge/ingredients/quercetin/
📋 Editorial information
Author: Prof. G. Pkhakadze, MD, MPH, PhD
Institution: Public Health Institute of Georgia (PHIG)
Affiliation: David Tvildiani Medical University (DTMU)
First published: January 2026
Last reviewed: 2026-05-29
Next review: April 2027
References: 4 cited sources
COI: SupplementIndex receives no funding from supplement manufacturers. All content independently authored by PHIG.
Process: Systematic literature review
📄 License & reuse
Published under Creative Commons Attribution 4.0 International (CC BY 4.0). You may share and adapt for any purpose with attribution.
Pkhakadze G. "Quercetin — Safety Profile." SupplementIndex, PHIG, 2026. https://supplement.ge/ingredients/quercetin/ CC BY 4.0.
GP
Prof. G. Pkhakadze, MD, MPH, PhD
Professor of Public Health · Head of Department, DTMU
Editor-in-Chief, Georgian Medical Journal (ISSN 3088-4322)
Chair, Public Health Institute of Georgia · UEMS Public Health Section
Educational and public health purposes. CC BY 4.0. Consult your healthcare provider before starting any supplement. Corrections: info@accreditation.ge. Publisher: PHIG