Quercetin and medications.
Quercetin is in the Distil supplement database, evidence Grade B. The page below lists every medication we have explicitly assessed it against.
Quercetin is a plant flavonoid found in onions, apples and capers, used for its anti-inflammatory, antioxidant and mast-cell-stabilising effects, which is why it shows up in allergy and immune stacks. Evidence is Grade B for immune and antioxidant support and Grade C for its much-hyped senolytic role, so the anti-ageing claims are the weakest part of the picture. Bioavailability is the catch: ordinary quercetin absorbs very poorly, so the phytosome form at 500 to 1,000mg is the one worth taking. The interaction list is where care is needed. Quercetin can interfere with fluoroquinolone antibiotics, and it inhibits CYP3A4, which means it can raise ciclosporin levels and should be excluded in transplant patients without their team's approval. The same CYP3A4 and P-gp effects mean it should also be avoided by anyone on antiretroviral therapy for HIV. At high doses it has mild antiplatelet activity and may affect warfarin metabolism, so flag it to your GP and monitor INR if you take an anticoagulant. It pairs well with vitamin C. Practically, separate it from those drug classes and review with a prescriber first.
Below are the 10 documented pairs we have explicitly assessed for Quercetin: 4 red and 6 amber. The pairs cluster around 3 mechanisms: CYP3A4 inhibition, Additive anticoagulation, and P-glycoprotein inhibition (raises drug levels). Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not listed here is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by medication, and the missing-item form at the bottom of the page routes any uncatalogued medication into our next curation pass.
Documented interactions
Last reviewed 14 June 2026. Each interaction below lists the evidence its assessment drew on: some rest on studies of the exact pair, others on mechanism evidence, where a citation may support one part of the reasoning rather than the exact combination. The evidence line on each entry says which.
CYP3A4 inhibition
Red Does interact with Ciclosporin?
Quercetin can slow how the body clears ciclosporin, which may push ciclosporin blood levels higher than intended. We treat this as a do-not-combine pair outside direct transplant-team supervision.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Red Does interact with Everolimus?
Quercetin can slow how the body clears everolimus, which may push everolimus blood levels higher than intended. We treat this as a do-not-combine pair outside direct transplant-team supervision.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Red Does interact with Sirolimus?
Quercetin can slow how the body clears sirolimus, which may push sirolimus blood levels higher than intended. We treat this as a do-not-combine pair outside direct transplant-team supervision.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Red Does interact with Tacrolimus?
Quercetin can slow how the body clears tacrolimus, which may push tacrolimus blood levels higher than intended. We treat this as a do-not-combine pair outside direct transplant-team supervision.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Atorvastatin?
Quercetin may slow how the body clears atorvastatin via CYP3A4, which can raise atorvastatin levels. Watch for muscle pain or unusual fatigue and tell your GP if you take both regularly.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Simvastatin?
Quercetin may slow how the body clears simvastatin via CYP3A4. Because simvastatin is more sensitive to CYP3A4 inhibition than atorvastatin, the effect may be larger. Watch for muscle pain and tell your GP if you take both.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Additive anticoagulation
Amber Does interact with Acenocoumarol?
High-dose quercetin may mildly add to the blood-thinning effect of acenocoumarol. The signal is weak. If you take acenocoumarol and use quercetin supplements, mention it to your anticoagulant clinic and watch for bruising.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Warfarin sodium?
Quercetin may, in theory, add to warfarin's blood-thinning effect at high doses, though a small human study found no change in INR. If you take warfarin, mention any high-dose quercetin to your GP and monitor your INR if you start it.
Evidence: Limited human data, based on case reports and a known mechanism.
P-glycoprotein inhibition (raises drug levels)
Amber Does interact with Digoxin?
Quercetin may slow how the body clears digoxin by blocking a transporter pump (P-glycoprotein), which can push digoxin levels higher. Digoxin has a narrow safe range, so if you take it, speak to your GP before adding quercetin and do not start a high-dose supplement without that conversation.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Fexofenadine hydrochloride?
Quercetin can raise blood levels of fexofenadine by blocking a transporter pump (P-glycoprotein). Fexofenadine is a low-risk antihistamine, so this rarely causes problems, but if you take both regularly and notice more drowsiness or side effects, separating them or lowering the quercetin dose is reasonable.
Evidence: Supported by human study data.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope. Use the checker below to surface any medication, and submit a missing item if you take something we have not catalogued.
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How we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
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The free checker answers one interaction question at a time. A Distil report reviews the bigger picture: your goals, diet, medications, current supplements and any blood results you provide, then shows what appears worth keeping, changing, adding or leaving out.
- what your diet already covers, so you are not adding a capsule for something food is already handling
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- how your medications and complete supplement stack fit together, with daily timing and a clear point for reassessment
The interaction check is one section of the full report. You also get the reasoning behind each recommendation and the evidence references used.
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