Skip to content
ppharmaranks
Menu
CompaniesProductsDrug classesConditionsBest by conditionTreatmentsInteraction checkerFood & medicinesWhat pharmacies payPill identifierMedicines & breastfeedingChildren’s dosage chartsDo medicines expire?Crushing & splitting pillsHow long meds take to workAlternating Tylenol & ibuprofenDrug recallsSupplementsSafety & lawsuitsGuidesA–ZHow we rate

quercetin

Quercetin is a dietary supplement.

Generic

Not yet rated· sourced from the FDA label
Rated against independent regulatory sources·Last updated June 23, 2026·How we rate
Verified againstopenFDANIH DailyMedRxClass
Check price on Amazon →We may earn a commission · never affects ratings

Key facts

Active ingredient
Quercetin
Form
Liquid
Type
Supplement

What the evidence says

What Quercetin is

Quercetin is a flavonol, a type of plant polyphenol (flavonoid). It occurs naturally in a range of foods such as onions, apples, berries, broccoli, citrus fruits, leafy herbs like cilantro and dill, tea, and red wine. Laboratory research suggests it may have antioxidant, anti-inflammatory, antiviral, and immune-modulating activity, but lab and test-tube findings do not establish clinical benefit. Quercetin has very low oral bioavailability (roughly 3-17%); per the NIH, taking it with sunflower lecithin can substantially raise absorption (reported as up to about 20 times in some research).

Commonly used for

General immune supportAntioxidantReducing inflammationStudied (with unclear results) for upper respiratory tract infections such as coldsStudied (inconclusively) for COVID-19

What the evidence shows

The available evidence does not establish that quercetin treats, cures, or prevents any illness. The NIH notes quercetin has been studied for reducing the risk or severity of upper respiratory tract infections, but "it's not clear whether it helps," and results across the few clinical trials have been mixed. For COVID-19, the NIH states the data are very limited and it is unclear whether quercetin reduces the risk or severity of disease because it has not been well studied. Marketing quercetin as a treatment, cure, or preventive for any disease is not supported by current evidence.

Typical dosage

There is no established or officially recommended supplement dose. Clinical trials referenced by the NIH have used 500 to 1,000 mg per day (sometimes combined with vitamin C or niacin), and the FDA considers up to 500 mg of quercetin per serving generally recognized as safe (GRAS) as an ingredient in foods and beverages. Because quercetin can interact with several medications and its benefits are unproven, talk with a clinician or pharmacist before starting it, especially if you take prescription drugs or have a health condition.

Safety

The NIH reports that no serious adverse effects have been reported in clinical trials of quercetin supplements using up to 1,000 mg/day for up to 12 weeks. Safety beyond these short study periods is not well characterized, and supplement quality is not tightly regulated. As with any supplement, people who are pregnant or breastfeeding and those with medical conditions should consult a healthcare provider before use.

Side effects

No serious side effects have been reported in studies of quercetin supplements at the doses tested. According to the NIH, quercetin supplements may, however, cause minor effects such as stomach pain, acid reflux, constipation, diarrhea, flatulence, and trouble sleeping. Data on long-term effects are limited, so it is reasonable to start cautiously and stop if you notice an adverse reaction.

Interactions & cautions

Quercetin may interact with several medications. The NIH notes it can affect drug-metabolizing enzymes (such as CYP3A4) and may raise blood levels of cyclosporine, pravastatin (a cholesterol medication), and fexofenadine (an antihistamine). It may add to the blood-pressure-lowering effect of antihypertensive medications, may interfere with drugs that suppress the immune system, and may inhibit platelet aggregation (relevant if you take blood thinners). Review all of your medications with a clinician or pharmacist before use.

Sources

This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Summarized from public health authorities; general reference, not medical advice. Talk to a licensed healthcare professional before starting any supplement.

Dosage forms

Liquid

The forms currently marketed in the U.S., per the FDA National Drug Code Directory.

Ways to save

Ask for the generic

Same active ingredient, far cheaper. Is there a generic? →

Request a 90-day supply

Bulk fills usually lower the per-dose price vs monthly refills.

Use copay cards

Manufacturer copay cards & patient-assistance programs — especially for brand drugs.

Compare alternatives

A same-class option may cost less. See alternatives →

Frequently asked questions

What forms does Quercetin come in?
Quercetin is currently marketed as liquid, per the FDA's National Drug Code Directory.

Information is sourced from public FDA regulatory data. Provided for general reference only — not medical advice. Always consult a licensed professional and the current prescribing information.

What people report to the FDA about Quercetin

The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 1,497 reports naming Quercetin, and the FDA flagged 52% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:

  • fatigue211 reports
  • headache119 reports
  • diarrhoea103 reports
  • nausea102 reports
  • dizziness93 reports
  • pruritus83 reports
  • arthralgia81 reports
  • dyspnoea79 reports

Read these as a signal, not a rate. A report does not mean Quercetin caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label.

Source: openFDA drug/event (FAERS), retrieved September 26, 2026.

Reviews

No reviews yet. Be the first to write one.

Write a review

Reviews are user opinions, not medical advice. Consult a licensed professional.

People also viewed

Rx72/100

cafcit

Caffeine Citrate

(20 data points)
~$2.55 /30View
Rx72/100

clonidine hydrochloride

Clonidine Hydrochloride

(14 data points)
~$1.05 /30View
Rx72/100

cromolyn sodium

Cromolyn Sodium

(9 data points)
$0.58 /mLView
Rx72/100

javadin

Clonidine Hydrochloride

(4 data points)
~$1.05 /30View
Rx72/100

loperamide hydrochloride

Loperamide Hydrochloride

(31 data points)
$0.05 /mLView
Rx72/100

modafinil

Modafinil

(6 data points)
~$10.45 /30View

Compare Quercetin head-to-head

Quercetin vs CafcitQuercetin vs Clonidine HydrochlorideQuercetin vs Cromolyn SodiumQuercetin vs JavadinQuercetin vs Loperamide Hydrochloride
Identify a pill by its imprint →Check a drug interaction →Drug recalls →

Browse medications A–Z

Research products from A to Z, compare independent ratings, and find alternatives.

quercetin

New
AlternativesCheck price on Amazon →