Quercetin
- Effective dose
- 500–1000 mg
- Evidence
- 3/5· Moderate
Last updated June 1, 2026
What it is
Quercetin is a plant flavonoid found in onions, apples, and tea, sold as a supplement for its antioxidant and anti-inflammatory properties. It scavenges free radicals and modulates inflammatory signaling, and is also marketed for immune and cardiovascular support. Its absorption from the gut is relatively poor, which is thought to limit how much reaches the bloodstream.
Benefits
In pooled trials, daily intake reduced blood pressure modestly (about 3 mmHg systolic, 2.6 mmHg diastolic), with the effect concentrated at doses of 500 mg/day or higher. Antioxidant and immune claims are common but less consistently supported.
When to take it
Taken once daily or split into two doses, often with food and a fat source to support absorption. Consistent daily use over weeks is typical in blood-pressure studies.
Side effects
Generally well tolerated; high doses (over 1,000 mg/day) have been linked to headache and tingling, and long-term very high intake may stress the kidneys. May interact with some antibiotics, blood thinners, and drugs processed by the liver's CYP enzymes.
Sources
Products containing Quercetin
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