Natural Compound

Quercetin

3,3′,4′,5,7-Pentahydroxyflavone

Evidence TierBWADA NOT PROHIBITED

tuneTypical Dose

500-1,000 mg/day

watchEffect Window

1-2 weeks for allergy symptoms. 4-8 weeks for blood pressure.

check_circleCompliance

WADA NOT PROHIBITED

Overview

Clinical Summary

Quercetin is a flavonoid found in onions and apples with anti-inflammatory and mast-cell stabilizing effects. It is used for allergy symptoms, vascular function, and exercise recovery biomarkers.

Trials suggest small vascular and lipid benefits in some cardiometabolic populations, and newer evidence also points to modest liver-enzyme and inflammatory improvements in MASLD. Allergy framing is still plausible mechanistically but clinically weaker and less standardized than the metabolic signal. Bioavailability remains a major limiter, so formulation matters.

Mast cell stabilizer that inhibits histamine release. Direct antioxidant and ROS scavenger. Inhibits COX/LOX inflammatory enzymes. Acts as a zinc ionophore for immune defense.

Outcomes

What This Is Expected To Influence

Primary Outcomes

  • Reduces blood pressure in hypertensive individuals (SBP/DBP)
  • Mast cell stabilization and histamine release reduction

Secondary Outcomes

  • Reduced URTI incidence in athletes under heavy physiological stress
  • Systemic antioxidant and anti-inflammatory activity

Safety

Contraindications and Interactions

Contraindications

  • Kidney disease or renal impairment (quercetin metabolites are renally excreted)
  • Known hypersensitivity to quercetin
  • Pregnancy considerations
  • Lactation considerations

Side effects

  • Headache and tingling (limited human reports)
  • Nausea, vomiting, and GI upset (stomach cramping, loose stool), especially above 1,000 mg/day
  • Rare kidney injury signal at high doses or non-oral exposure

Interactions

  • CYP3A4, CYP2C8, CYP2C9, and CYP2E1 substrates (possible increased drug exposure)
  • Cyclosporine, diclofenac, fexofenadine, midazolam, statins (atorvastatin/simvastatin/pravastatin), and other OATP1B1 substrates
  • Anticoagulants or antiplatelet agents (e.g., warfarin) may increase bleeding risk
  • Fluoroquinolone antibiotics (e.g., ciprofloxacin, levofloxacin). Avoid concurrent high-dose use due to possible reduced antibiotic activity

Avoid if

  • Pregnancy considerations
  • Lactation considerations
  • Pre-existing kidney disease, severe renal impairment, or active kidney stone recurrence
  • People using CYP3A4/CYP2C8/CYP2C9/CYP2E1 substrate medications
  • People using cyclosporine, diclofenac, fexofenadine, midazolam, or statins (atorvastatin/simvastatin/pravastatin)
  • Concurrent high-dose fluoroquinolone therapy

Evidence

Study-level References

quercetin-SRC-001Meta-analysis of RCTs
Sourceopen_in_new

Serban MC, et al. "Effects of Quercetin on Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials." J Am Heart Assoc. 2016.

Population: Adults (hypertensive and normotensive)

Key findings: Meta-analysis showed significant reductions in both systolic and diastolic blood pressure with quercetin supplementation, particularly at doses of 500 mg/day and above.

Paper content

Meta-analysis showed significant reductions in both systolic and diastolic blood pressure with quercetin supplementation, particularly at doses of 500 mg/day and above.

quercetin-SRC-002Meta-analysis of randomized controlled trials
Sourceopen_in_new

Popiolek-Kalisz J, Fornal E. The Effects of Quercetin Supplementation on Blood Pressure - Meta-Analysis. Curr Probl Cardiol. 2022;47(11):101350. doi:10.1016/j.cpcardiol.2022.101350. PMID:35948195.

Population: Normotensive and prehypertensive or hypertensive adults across randomized trials.

Dose protocol: Randomized trials through May 2022 in normotensive and prehypertensive or hypertensive adults.

Key findings: Updated meta-analysis found small reductions in systolic and diastolic blood pressure, confirming a modest vascular effect rather than a large antihypertensive effect.

Notes: Modernizes the BP claim and keeps the magnitude realistic.

Paper content

Quercetin produced small reductions in systolic and diastolic blood pressure across randomized trials, supporting a modest vascular effect rather than a drug-like antihypertensive response.

quercetin-SRC-003Systematic review and meta-analysis of randomized controlled trials
Sourceopen_in_new

Jin D, Jin S, Zhou T, et al. Effects of Quercetin on Metabolic Dysfunction-Associated Steatotic Liver Disease: A Systematic Review and Meta-Analysis. Food Sci Nutr. 2025;13(12):e71358. doi:10.1002/fsn3.71358. PMID:41404533.

Population: Patients with metabolic dysfunction-associated steatotic liver disease across seven randomized controlled trials.

Dose protocol: Oral quercetin across seven randomized MASLD trials

Key findings: Reduced liver enzymes, CRP, total cholesterol, LDL, and triglycerides, with HDL improvement.

Notes: Useful modernization of the cardiometabolic evidence base, but certainty is still limited.

Paper content

This 2025 meta-analysis modernizes quercetin’s evidence base beyond the older blood-pressure framing. In MASLD patients, quercetin improved liver enzymes, C-reactive protein, and several lipid markers, which supports a broader but still cautious cardiometabolic interpretation. The certainty of evidence ranged from very low to moderate, so these effects should be framed as promising rather than settled.

quercetin-SRC-004Randomized, double-blind, placebo-controlled trial.
Sourceopen_in_new

Mury P, Dagher O, Fortier A, et al. Quercetin Reduces Vascular Senescence and Inflammation in Symptomatic Male but Not Female Coronary Artery Disease Patients. Aging Cell. 2025;24(8):e70108. doi:10.1111/acel.70108. PMID:40375481.

Population: Patients undergoing coronary artery bypass graft surgery.

Dose protocol: Quercetin 1000 mg/day for 2 days pre-surgery through discharge in 97 CABG patients.

Key findings: Improved endothelial function (mainly in men), reduced post-operative atrial fibrillation from 18% to 4%, and reversed vascular senescence transcriptomic signatures.

Notes: Short perioperative intervention limits generalizability, but direct human vascular evidence is strong.

Paper content

This double-blind placebo-controlled trial tested quercetin 1000 mg/day in 97 patients undergoing coronary artery bypass graft surgery. Quercetin improved endothelial function overall, reversed vascular senescence pathways (primarily in men), and reduced post-operative atrial fibrillation incidence from 18% to 4% compared to placebo. The benefit was sex-specific, with minimal endothelial improvement in female patients. This trial provides direct human vascular evidence for quercetin in a high-risk cardiovascular population, though the short intervention window and surgical context limit generalizability to chronic supplementation.

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