Quercetin is a flavonoid found in foods such as onions, kale and apples. Sold as a supplement, quercetin is promoted to help with a range of conditions, from prostatitis and asthma, to lowering blood sugar and reducing the pain of arthritis. But do quercetin supplements really work, and if so, which products are best? We carefully reviewed the evidence and tested popular quercetin and quercetin dihydrate supplements on the market, including several capsules, a powder, and a liquid. Each product was tested for its amount of quercetin and checked for contamination with heavy metals.
Our tests revealed that two products contained 12% to 14% less quercetin than listed on their labels. We also found that you can spend as little as 11 cents to as much as $1.17 to get the same amount of quercetin, so it pays to choose wisely.
Among the products that passed all of our tests, we selected Top Picks for quercetin supplements based on quality and cost.
You must be a member to get the full test results, along with ConsumerLab's recommendations. You'll get results for seven products -- six selected by ConsumerLab and one other that passed the same testing through our voluntary Quality Certification Program.
In this comprehensive review, you'll discover:
- Which quercetin supplements passed or failed our tests
- ConsumerLab's Top Picks for the best quercetin supplements
- The evidence for or against quercetin for prostatitis, insulin resistance, rheumatoid arthritis, lowering blood pressure, and other uses
- What to look for on quercetin labels
- Quercetin dosage for specific uses
- The best way to take quercetin to improve absorption and reduce stomach upset
- Cautions, potential side effects, and drug interactions with quercetin supplements