Quercetin
Also known as: Quercetin dihydrate, Quercetin aglycone
Quercetin shows antioxidant, anti-inflammatory and senolytic activity in vitro and in animals. Human trials are heterogeneous; exercise and upper-respiratory-infection studies show context-dependent, modest effects. Plain quercetin's poor absorption limits systemic exposure.
Last reviewed: 2026-10-06 · 0 indexed studies
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Overview
Quercetin is a flavonol found in onions, apples and berries. Supplemental quercetin (often the dihydrate form) is positioned for immune support and antioxidant activity; oral bioavailability of the plain aglycone is low, driving interest in phytosome and glycoside forms.
Mechanism & Function
Mechanism of Action
Scavenges free radicals, modulates NF-κB and inflammasome signalling (preclinical), and inhibits histamine release from mast cells. Senolytic activity (clearing senescent cells) is preclinical.
Physiological Role
No physiological role; a dietary flavonoid.
Primary Pathways
Performance / Health Relevance
Studied in athletes for illness risk after heavy exertion; effects are modest and inconsistent.
Evidence Review
No human clinical studies indexed for this ingredient yet.
No meta-analyses or systematic reviews indexed for this ingredient yet.
Dimensions marked N/A have no indexed evidence of that class. They are shown as unavailable rather than scored.
Practical Use & Dosage
- Minimum Effective Dose
- 500 mg/day (plain form)
- Optimal Range
- 500–1,000 mg/day
- Upper / Caution Level
- Up to 1,000 mg/day commonly used; long-term high-dose data limited
- Timing
- Daily, with meals
- Best Format
- Phytosome or isoquercetin forms have better bioavailability than plain dihydrate
- Bioavailability
- Plain quercetin is poorly absorbed (<2% estimated); enhanced forms improve exposure several-fold.
- Absorption Considerations
- Co-ingestion with fat improves absorption of plain forms.
Safety & Interactions
Side Effects
- •Rare headache
- •Rare GI upset
- •Kidney concerns at very high doses (theoretical)
Contraindications
- Kidney disease (high doses)
Drug Interactions
- •CYP3A4 and P-gp substrates (quercetin can inhibit these — may raise levels of some drugs)
- •Antibiotics (fluoroquinolones, theoretical)
Who Should Avoid
- •People on narrow-therapeutic-index drugs metabolised by CYP3A4, without medical advice
Monitoring
Review medications for CYP3A4/P-gp interactions.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is Quercetin typically used or indicated?
Quercetin is most commonly used for: Antioxidant and immune-support formulas, Healthy-ageing blends, Allergy-season supplements. No physiological role; a dietary flavonoid.
How does Quercetin work?
Scavenges free radicals, modulates NF-κB and inflammasome signalling (preclinical), and inhibits histamine release from mast cells. Senolytic activity (clearing senescent cells) is preclinical.
What is the recommended dose of Quercetin?
The optimal range is 500–1,000 mg/day. with a minimum effective dose of 500 mg/day (plain form). Best taken: Daily, with meals. Upper / caution level: Up to 1,000 mg/day commonly used; long-term high-dose data limited.
What are the side effects of Quercetin?
Reported side effects include: Rare headache; Rare GI upset; and Kidney concerns at very high doses (theoretical). Monitoring: Review medications for CYP3A4/P-gp interactions.
Does Quercetin interact with medications?
Known or theoretical interactions: CYP3A4 and P-gp substrates (quercetin can inhibit these — may raise levels of some drugs); and Antibiotics (fluoroquinolones, theoretical). Always check with a clinician before combining with prescription medication.
Who should avoid Quercetin?
Quercetin is generally not recommended for: People on narrow-therapeutic-index drugs metabolised by CYP3A4, without medical advice; and Kidney disease (high doses).
How strong is the evidence for Quercetin?
Evidence level: Limited (overall score 35/100), based on 0 indexed studies on SuppIndex.
Research & References (0)
No studies match this filter
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Research Overview
Limited EvidenceCite this ingredient
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Stable URL
https://thesuppindex.com/ingredients/quercetin
SuppIndex. (2026). Quercetin: Evidence summary, dosage and clinical studies. Retrieved October 16, 2026, from https://thesuppindex.com/ingredients/quercetin
Based on 0 indexed studies · Evidence level: Limited.
Goal Ratings
Stack Compatibility
Often paired with vitamin C, bromelain or zinc in immune formulas.