Overview
Quercetin is a plant pigment (flavonoid). It’s found in many plants and foods, such as red wine, onions, green tea, apples, and berries.
Quercetin has antioxidant and anti-inflammatory effects that might help reduce swelling, kill cancer cells, control blood sugar, and help prevent heart disease.
Quercetin is most commonly used for conditions of the heart and blood vessels and to prevent cancer. It is also used for arthritis, bladder infections, and diabetes, but there is no strong scientific evidence to support most of these uses. There is also no good evidence to support using quercetin for COVID-19.
Uses & Effectiveness
Possibly Ineffective for
Athletic performance. Taking quercetin by mouth before exercise doesn’t decrease fatigue or improve exercise ability.
There is interest in using quercetin for a number of other purposes, but there isn’t enough reliable information to say whether it might be helpful.
Side Effects
When taken by mouth: Quercetin is possibly safe for most people when used short-term. Quercetin has been safely used in doses up to 1 gram daily for 12 weeks. It’s not known if long-term use or higher doses are safe.
When applied to the skin: There isn’t enough reliable information to know if quercetin is safe or what the side effects might be.
Special Precautions and Warnings
When taken by mouth: Quercetin is possibly safe for most people when used short-term. Quercetin has been safely used in doses up to 1 gram daily for 12 weeks. It’s not known if long-term use or higher doses are safe.
When applied to the skin: There isn’t enough reliable information to know if quercetin is safe or what the side effects might be. Pregnancy and breast-feeding: There isn’t enough reliable information to know if quercetin is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.
Kidney problems: Quercetin might make kidney problems worse. Don’t use quercetin if you have kidney problems.
Dosing
Quercetin has most often been used by adults in doses of 250-1000 mg by mouth daily for up to 12 weeks. Speak with a healthcare provider to find out what dose might be best for a specific condition.