What is it used for?
Source of (an) antioxidant(s)/Provides (an) antioxidant(s) [Source note 2].
Source of (an) antioxidant(s)/Provides (an) antioxidant(s) that help fight/protect (cell) against/reduce (the oxidative effect of/the oxidative damage caused by/cell damage caused by) free radicals [Source note 3].
Used in Herbal Medicine as a capillary/blood vessel protectant [Source note 4].
Note: If Quercetin is combined with other active ingredients with antioxidant properties, there is an option to use the antioxidant claims in plural. The singular should be used when the product only contains one chemical substance (e.g., Quercetin) as the active ingredient associated with the antioxidant claim.
Who does this guide cover?
Adults 18 years and older
How is it taken?
Oral
Which forms are covered?
this reference excludes foods or food-like dosage forms as indicated in the Compendium of references Guidance Document.
Quantities
Antioxidant
Not to exceed 1,200 milligrams of Quercetin, per day and 600 milligrams per single dose [Source note 5].
Capillary/ blood vessel protectant
600 - 1,200 milligrams of Quercetin, per day. Not to exceed 600 milligrams per single dose [Source note 6].
Note: Must not exceed 600 milligrams of Citrus bioflavonoids, per day, when combined with other bioflavonoids such as but not limited to, Citrus bioflavonoids, hesperidin, rutin, etc.
How is it used?
Products providing 40 milligrams or more Quercetin, per day
Take with a meal/food [Source note 7].
How long is it used?
Products providing 40 milligrams or more Quercetin, per day
Ask a healthcare professional for use beyond 12 weeks [Source note 8].
Warnings and precautions
Products providing 40 milligrams or more Quercetin, per day
Ask a healthcare professional before use if you are pregnant or breastfeeding.
When should it be avoided?
The reference does not require an additional label statement in this section. This does not establish an absence of risk.
Possible side effects
The reference does not require an additional label statement in this section. This does not establish an absence of risk.
Storage
Must be established in accordance with the requirements described in the applicable product regulations.
Preparation details
Ingredient identity, preparation requirements, and other details that define the scope of this guide.
Ingredients and preparations
| Proper name(s) | Common name(s) | Source information / Source ingredient(s) |
|---|---|---|
|
|
|
References: Proper names: NIH 2025; Brayfield and Cadart 2024; RSC 2024; Common names: NIH 2025; RSC 2024; Source information: source ingredient database 2026.
Other ingredients
Must be chosen from the current source ingredient database and must meet the limitations outlined in the database.
Preparation and quality requirements
The finished product specifications must be established in accordance with the requirements described in the source authority source’s product quality guidance.
The active ingredient must comply with the requirements outlined in the source ingredient database.
Guide change history
Updates to this SupplementSafety.org guide.
Minor updates
Updated guide wording, organization, and source presentation. Added our editorial change history.
Initial release
Initial SupplementSafety.org guide prepared from source reference material.
Validation: Not yet completed. Editorial updates do not constitute clinical validation.
Sources
Source information
This guide organizes source material about uses, preparations, amounts, and precautions. Read the conditions alongside each statement; the information may apply only to particular preparations or populations.
The source document includes supporting references. We have not independently summarized or assessed every cited study for this guide.
- Source document version
- January 30, 2026
- Source captured
- Aug 15, 2026
- Editorial work
- Editorial preparation. Independent clinical review has not been recorded for this guide.
Full citations are available through the link above. Verification is required to open them; reading this guide does not require verification.
Taking a medication too?
Explore our supplement–medication interaction checker. Its coverage and review status are shown with the results; a missing finding does not establish that a combination is safe.