Ingredient guide
Quercetin is a plant flavonoid found in onions, apples, and tea. Meta-analyses show it can modestly lower blood pressure at doses of 500 mg per day or more. Most claims for allergy and immune support rest on early or laboratory evidence.
Moderate evidenceQuercetin is one of the most abundant flavonoids in the human diet. You get it from onions, apples, tea, capers, and red wine. As a supplement it is concentrated and sold at doses far higher than you would ever eat. Its absorption is famously poor, which is why some products use a fat-bound form called a phytosome to help it cross into the blood.
Quercetin acts as an antioxidant, soaking up reactive molecules, and influences inflammatory signalling in laboratory studies. It also appears to relax blood vessels and reduce stickiness of platelets at higher doses. The blood pressure and antioxidant actions are the strongest threads in the science.
For blood pressure, a meta-analysis of randomised trials found that quercetin lowered blood pressure, with the effect appearing at doses of 500 mg per day or more. Drops of a few mmHg were reported in people with hypertension. The mechanism is not fully settled, but the signal is real and reasonably consistent.
Beyond blood pressure, claims for allergy, exercise recovery, and immune support are popular but rest mostly on laboratory and small human studies. Recovery trials show tiny effects at best. We grade the overall human evidence as moderate, strongest for blood pressure and weaker for the broader claims. Poor absorption is a real practical limit at lower doses.
For a blood pressure effect, the research points to 500 mg to 1,000 mg per day, often split, for several weeks. Improved-absorption forms can use lower doses. Because quercetin can change how some medicines are processed and very high intravenous doses have caused harm, check with a healthcare provider first if you take regular medicine.
Blood pressure trials commonly use 500 mg to 1,000 mg of quercetin per day, often split, for several weeks. Quercetin is poorly absorbed, so newer phytosome forms are sold for better uptake. Ask your healthcare provider before regular use if you take blood pressure medicine or have kidney concerns.
A meta-analysis of trials shows a small reduction at 500 mg per day or more, with the clearest effect in people with raised pressure.
Laboratory studies show effects on histamine-releasing cells, but solid human trials are limited. It is a popular use without strong human evidence.
It does not dissolve well in water. That is why phytosome and other fat-bound forms are sold, with the aim of getting more into the bloodstream from a smaller dose.
Blood pressure trials use 500 to 1,000 mg per day. Improved-absorption forms can use less. Talk to a healthcare provider about the right form for you.
