Evidence

DISCLAIMER: These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Cardiovascular disease: Several of the effects of flavonoids that have been observed in laboratory and animal studies suggest that they might be effective in reducing cardiovascular disease risk. Studies in humans using polyphenolic compounds from red grapes showed improvement in endothelial function in patients with coronary heart disease. Antioxidant and cholesterol-lowering effects are proposed.
Grade: C

Immune function (after intense exercise): Quercetin does not appear to affect changes in the immune system caused by intense exercise. However, it reduced the number of respiratory tract infections in people who participated in intense cycling. More research is needed.
Grade: C

Pancreatic cancer prevention: Some research suggests that quercetin may help prevent pancreatic cancer in smokers. However, quercetin did not have this effect in non-smokers or former smokers. More research is needed to determine if quercetin is beneficial.
Grade: C

Prostatitis/chronic pelvic pain syndrome: There is some evidence that quercetin may be useful for the treatment of chronic prostatitis and chronic pelvic pain syndrome. Further research is needed to confirm these results.
Grade: C

Tradition

WARNING: DISCLAIMER: The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Dosing

Adults (over 18 years old)

It has been suggested that quercetin should be taken 20 minutes before meals. Quercetin has been ingested from onions, juice, black tea, and red wine. Doses of 100-500 milligrams of quercetin have been taken 2-3 times daily. It is available in tablet, capsule, or softgel form. Intravenous and intramuscular forms have been injected by a healthcare provider.

Children (under 18 years old)

Insufficient available evidence to recommend.