NutriStack
Quercetin and Warfarin, a caution.
Quercetin and its metabolites strongly displace warfarin from human serum albumin, which can transiently raise free (active) warfarin concentrations. High-dose quercetin supplements also inhibit CYP2C8/2C9/3A4 to varying degrees. The combination has been associated with increased bleeding risk in herbal product–warfarin reviews.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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At a glance
- Pair type
- Caution
- Evidence (highest tier)
- Emerging
- Source citations
- 2 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Emerging evidence
Caution
What is happening. Quercetin and its metabolites strongly displace warfarin from human serum albumin, which can transiently raise free (active) warfarin concentrations. High-dose quercetin supplements also inhibit CYP2C8/2C9/3A4 to varying degrees. The combination has been associated with increased bleeding risk in herbal product–warfarin reviews.
Mechanism. Quercetin glucuronide and sulfate metabolites bind the warfarin site on human serum albumin, displacing protein-bound warfarin and increasing the free fraction. Quercetin and its metabolites also inhibit several CYP isoforms including CYP2C9 and CYP3A4, the enzymes responsible for warfarin metabolism.
Recommendation. Avoid high-dose quercetin supplements (500 mg or more per day) on warfarin. Dietary intake from fruits and vegetables is fine. If you start a quercetin supplement, tell your anticoagulation clinic and ask for INR re-check within 1-2 weeks.
Sources (2)
- Poór M, Boda G, Needs PW, Kroon PA, Lemli B, Bencsik T. Interaction of quercetin and its metabolites with warfarin: Displacement of warfarin from serum albumin and inhibition of CYP2C9 enzyme. Biomed Pharmacother. 2017;88:574-581. PMID 28135601
- Tan CSS, Lee SWH. Warfarin and food, herbal or dietary supplement interactions: A systematic review. Br J Clin Pharmacol. 2021;87(2):352-374. PMID 32478963
Stack Score
How this pair moves the number.
Effect on the composite score
If both Quercetin and Warfarin are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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