Rankings / Immune & Inflammation

Quercetin

Immune & Inflammation · Flavonoid

Tier C+

Reviewed by Read Off Label · Last reviewed · How we grade

mtor-inhibitionampkpolyphenolantioxidantotcsenolyticanti-inflammatory
5.5 / 10
Tier C+
Ev 3 Bn 3.5 Sf 9

Bottom line

Read Off Label grades Quercetin as C+ (5.5/10) based on weak evidence, low-med benefit magnitude, and a low-risk safety profile.

Native quercetin has <1% oral bioavailability — most trials use large doses or enhanced formulations.

Studied, labeled, or reported-use context: 500-1000 mg/day; phytosome form at lower doses — OTC; not individualized guidance.

What the evidence says

Native quercetin has <1% oral bioavailability — most trials use large doses or enhanced formulations. The 'zinc ionophore' claim popularized during COVID was based on weak in vitro data. Small studies report mast-cell and allergic-symptom effects; clinical outcome evidence is limited.

Mechanism

Flavonol ubiquitous in plants (onions, apples, capers); broad antioxidant; mast cell stabilization; proposed zinc ionophore activity (controversial claims during COVID); mTOR/AMPK modulation

Studied, labeled, or reported dose & route

500-1000 mg/day; phytosome form at lower doses

This records doses and routes described in studies, approved labeling, clinical practice, or documented use. It is not individualized guidance and does not establish safety; context changes with indication, formulation, health history, monitoring, and other medicines.

Citations

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Common questions

What does the evidence show about Quercetin's effects?
Read Off Label rates the evidence for Quercetin as Weak and the benefit magnitude as low-med, producing an overall grade of C+ (5.5/10). Native quercetin has <1% oral bioavailability — most trials use large doses or enhanced formulations.
What safety findings are reported for Quercetin?
Quercetin has a low risk profile in the database. Low (very low bioavailability native; enhanced forms — quercetin phytosome, EMIQ — better absorbed; rare renal toxicity reported at chronic high doses) Legal status: OTC.
What doses or routes are reported for Quercetin?
500-1000 mg/day; phytosome form at lower doses This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.
How does Quercetin work?
Flavonol ubiquitous in plants (onions, apples, capers); broad antioxidant; mast cell stabilization; proposed zinc ionophore activity (controversial claims during COVID); mTOR/AMPK modulation

This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.