What it does
A flavonoid present in onions, apples and other plant foods.
What symptoms can—and cannot—tell you
There is no established dietary deficiency syndrome for this specific botanical or compound. Symptoms are not evidence that you need this supplement.
Food sources
Onions, apples, berries and other plant foods.
Supplement forms
Quercetin dihydrate and formulated quercetin products.
Before taking a supplement
Concentrated supplements can interact with medicines and may differ substantially from foods. Discuss pregnancy, breastfeeding, kidney or liver disease, and planned surgery with a clinician or pharmacist.
Questions for your visit
Could my diet, medicines, absorption or another condition explain my concern? What evidence would support treatment, and how would we check whether it helps?
Names you may see
Quercetin
Sources & perspective
This is an editorial adaptation of the Purser Wellness nutrient reference app. Purser teaching connections are labeled separately from clinical interpretation. Private cases and individual treatment protocols are not reproduced.
The external resource below explains supplement safety; it does not validate every proposed use of this ingredient.
NCCIH: using dietary supplements wisely