Summary
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What are quercetin and rutin?
Quercetin is a yellow-colored flavonoid found in plant-based foods such as capers, onions, and kale. In its natural form it is attached to sugar molecules and known as rutin (which is 49.5% quercetin). Supplements may contain rutin, or quercetin itself, or quercetin attached to water molecules (as quercetin dihydrate, which is about 90% quercetin). Interestingly, the absorption of quercetin from the gut appears to be greater from quercetin- and rutin-containing foods than from supplements. See What It Is. -
How are quercetin and rutin used?
Many short-term and relatively small clinical studies have been conducted with quercetin, suggesting modest benefit in conditions such as prostatitis, insulin resistance, rheumatoid arthritis, and in preventing or treating viral illness. Quercetin may also modestly reduce blood pressure. It has also been tried for allergy, viral infection, sleep, memory, and cancer. There has not been much clinical study of rutin as a stand-alone supplement — it has mainly been studied within a multi-ingredient product. See What It Does. -
What did CL's tests of quercetin and rutin supplements find?
CL's tests revealed that one rutin supplement contained only 17.4% of its listed rutin and one other fell short at just 88.7% of what it promised. Overall, the cost to obtain quercetin (or potential quercetin from rutin) ranged from as little as 16 cents to $6.41! See What CL Found. 
Top Picks for quercetin and rutin:
Based on quality and cost, ConsumerLab selected two Top Picks for quercetin and one Top Pick for rutin.-
How much quercetin or rutin should I take and when?
Typical dosage of quercetin is 500 mg taken once or twice daily. There is less known about dosage with rutin. To enhance absorption, it is best to take quercetin or rutin with a meal containing fats or oils. See the ConsumerTips™ section for the dosage for specific uses.
Be aware that you can also get quercetin and rutin naturally from foods — and absorption may be higher from food than supplements. Also note that a form of quercetin called EMIQ is touted as having 40 times greater absorption than quercetin, but this is not an accurate claim. -
Quercetin and safety and side effects:
Side effects of quercetin are uncommon and generally mild. However, quercetin may interact with a variety of prescription medications. As quercetin is a major component of rutin, similar concerns apply to rutin. For details, see Concerns and Cautions.
