bleeding
27 interactions related to bleeding
warfarin + dong quai
Dong quai (Angelica sinensis) contains coumarin-family compounds (ferulic acid, osthole) and has antiplatelet activity in laboratory studies. A published case report described a previously stable warfarin patient whose INR climbed well above her target range within weeks of adding dong quai, then returned to normal after she stopped it. The signal rests on a single human case plus animal data, so it is taken seriously but is not extensively documented.
apixaban + fish oil
Apixaban is a direct factor Xa inhibitor that raises bleeding risk on its own. Omega-3 fatty acids in fish oil have a mild antiplatelet effect that can theoretically add to that risk. A large 2024 systematic review and meta-analysis found that typical supplement-level omega-3 intake did not significantly raise bleeding risk, with only a small absolute increase seen at very high, prescription-strength doses. Standard fish oil is generally compatible with apixaban when the prescriber is aware, while high-dose omega-3 should be cleared with a clinician.
warfarin + danshen
Danshen (Salvia miltiorrhiza), widely used in traditional Chinese medicine for cardiovascular conditions, interacts with warfarin on two fronts. It slows warfarin's clearance (a pharmacokinetic effect that raises warfarin levels) and independently inhibits platelets and clotting (a pharmacodynamic effect). Published case reports describe severe over-anticoagulation and serious bleeds, including bleeding into the chest cavity, when patients added danshen to warfarin.
warfarin + feverfew
Feverfew (Tanacetum parthenium) inhibits platelet aggregation in laboratory studies via its parthenolide sesquiterpene lactones, which creates a theoretical, additive bleeding concern alongside warfarin. The evidence is bench/in-vitro only: systematic reviews classify feverfew's anticoagulant signal as low-level laboratory evidence, and there are no published human case reports of bleeding when feverfew is combined with warfarin. The cautious, mechanism-based approach is to avoid concentrated feverfew supplements while on warfarin and to disclose use to the clinician managing anticoagulation.
aspirin + ginkgo
Ginkgo biloba can inhibit platelet-activating factor (PAF) and platelet aggregation, which may add to aspirin's irreversible inhibition of cyclooxygenase-1 and thromboxane A2. Observational data suggest a modest increase in minor bleeding events when the two are combined, and there are case reports of more serious bleeds in vulnerable patients, though a controlled trial found no measurable added effect on platelet function.
rivaroxaban + fish oil
Omega-3 fatty acids in fish oil have a mild antiplatelet effect, slightly shifting platelet thromboxane production and modestly lengthening bleeding time. Rivaroxaban blocks Factor Xa to reduce clotting. The two act through different pathways, so the combination is additive in theory, but clinical evidence suggests the real-world bleeding effect is small. A large randomized trial found no increase in bleeding even with high-dose fish oil.
rivaroxaban + ginkgo
Rivaroxaban is a Factor Xa inhibitor and ginkgo has mild antiplatelet activity, so combining them was theorized to add to bleeding risk. However, a controlled trial in healthy subjects found standardized EGb 761 ginkgo extract did not change rivaroxaban's pharmacokinetics, anti-Factor Xa activity, or coagulation parameters, and caused no bleeding-related adverse events.
aspirin + fish oil
Omega-3 fatty acids in fish oil mildly reduce platelet aggregation, which in theory adds to aspirin's antiplatelet effect. In practice, clinical studies have not found a clinically significant increase in major bleeding when standard fish oil is combined with aspirin.
green tea + warfarin
Green tea leaves contain vitamin K, the cofactor the liver needs to make the clotting factors warfarin works against. Large or fluctuating green tea intake can lower the INR and weaken warfarin's anticoagulant effect, as documented in a published case report. Moderate, steady intake is generally not a problem.
alcohol + warfarin
Alcohol affects warfarin in two opposing directions: acute heavy drinking slows the liver's metabolism of warfarin, which can raise INR and bleeding risk, while sustained heavy drinking induces those same enzymes and can lower INR, increasing clot risk. Alcohol also impairs platelets and can damage the liver where clotting factors are made, and intoxication raises fall risk, all of which compound the bleeding hazard.
warfarin + ginger
Ginger has a mild antiplatelet effect that can add to warfarin's anticoagulant effect. Case reports describe a rise in INR after a person on stable warfarin started a daily ginger supplement, with the INR returning to range once the supplement was stopped. Ginger used in cooking and the occasional ginger tea is a food-level exposure and is generally considered safe.
warfarin + ginkgo
Warfarin and ginkgo act on clotting through different pathways, raising a plausible but not firmly proven bleeding concern.
warfarin + turmeric
Curcumin, the main active in turmeric, has antiplatelet activity that can add to warfarin's effect and raise bleeding risk. New Zealand's medicines regulator, Medsafe, issued an alert in 2018 after a patient stable on warfarin had their INR climb to a dangerously high level within weeks of starting a turmeric/curcumin product. A possible effect on the enzyme that clears warfarin has been seen only in animal and laboratory studies, not in people.
clopidogrel + ginkgo
Clopidogrel blocks the platelet P2Y12 ADP receptor, while ginkgo biloba inhibits platelet-activating factor through a separate pathway. A controlled healthy-volunteer study found no measurable added platelet inhibition, but case reports and an observational analysis link the combination to bleeding. The realistic concern is a modest, additive bleeding risk, most relevant in older patients and those also taking aspirin.
matcha + warfarin
Matcha is powdered whole green tea leaf, so each serving delivers more vitamin K than a brewed cup of green tea. Vitamin K is the cofactor warfarin works against, so starting, stopping, or varying a matcha habit can shift your INR and change how well warfarin protects you. The effect is documented for green tea and extends to matcha through its whole-leaf vitamin K content.
cranberry + warfarin
Cranberry contains flavonoids and polyphenols that may slow CYP2C9, the liver enzyme that clears the more potent S-enantiomer of warfarin. Multiple human case reports describe a rising INR and serious bleeding in patients who took up cranberry juice or supplements while stably anticoagulated, and the effect appears to depend on how much cranberry is consumed: randomized trials using a modest daily amount have not consistently reproduced it.
cayenne + warfarin
Capsaicin, the active constituent in cayenne (Capsicum), is theorized to add modestly to warfarin's blood-thinning effect through additive antiplatelet activity and possible effects on drug metabolism. The interaction is mechanistic; no human bleeding cases specific to cayenne plus warfarin have been documented, and interaction databases classify it as minor.
cinnamon + warfarin
Concentrated cassia cinnamon supplements are a major source of coumarin, a compound that can be hard on the liver and may interfere with how the body clears warfarin. Because warfarin has a very narrow safety margin, even small shifts can raise bleeding risk, and case reports describe elevated INR when cinnamon-containing products were added to stable warfarin therapy.
fenugreek + warfarin
Fenugreek (Trigonella foenum-graecum) contains coumarin-related compounds and has shown anticoagulant activity in laboratory studies. A published case report describes a rise in INR when a boldo-fenugreek combination product was added to stable warfarin therapy, with INR normalizing on discontinuation and rising again on rechallenge. The evidence is limited to that single case plus mechanistic plausibility, so the interaction is treated as plausible rather than firmly established.
turmeric tea + warfarin
Curcumin, the main active compound in turmeric, has antiplatelet and anticoagulant activity in laboratory studies and may inhibit the liver enzymes that clear warfarin. Regulatory case reports describe stable warfarin patients whose INR rose into a dangerous, emergency range within weeks of starting a turmeric product. The published evidence is limited to a small number of case reports, but the bleeding signal is consistent enough to warrant caution.
chamomile tea + warfarin
Chamomile contains naturally occurring coumarin-type compounds and may slow the liver enzymes that clear warfarin, so heavy or sudden chamomile use could add to warfarin's blood-thinning effect. A published case report linked frequent chamomile tea and lotion use to a dangerously high INR and severe internal bleeding in an older woman whose warfarin had previously been stable.
flaxseed + warfarin
Flaxseed is rich in alpha-linolenic acid, an omega-3 fat with a mild antiplatelet effect, and in soluble fiber that can theoretically bind oral medicines in the gut. Both mechanisms could in principle nudge warfarin's bleeding risk or absorption, but no case of an actual flaxseed-warfarin bleed or INR shift has been documented. The concern is mechanistic and the practical risk from culinary amounts is low.
cocoa + warfarin
Cocoa flavanols can modestly reduce platelet activity in people, which in theory could add to warfarin's anticoagulant effect. In practice the evidence is mechanistic only: no case reports or clinical studies show actual bleeding or a change in INR from cocoa in people taking warfarin. Keeping cocoa intake small and consistent is a sensible precaution rather than a response to a proven interaction.
clopidogrel + garlic
Clopidogrel blocks the platelet P2Y12 ADP receptor to prevent clots. Concentrated garlic supplements also have a mild antiplatelet effect through sulfur compounds such as allicin and ajoene. Taken together, the antiplatelet effects can add up and may modestly raise bleeding risk, especially before procedures. Culinary garlic in food amounts is not a meaningful concern.
fluconazole + warfarin
Fluconazole inhibits CYP2C9, the main enzyme that clears warfarin, so it can sharply raise warfarin's blood-thinning effect within a few days of starting, even after a single antifungal dose. Case reports document this combination causing serious and sometimes fatal bleeding.
chia seeds + blood thinners
Chia seeds contain plant-form omega-3 (alpha-linolenic acid) and soluble fiber. The omega-3 has a mild, mostly theoretical effect on platelets, and the fiber gel could slow a pill's absorption if eaten at the same time. There is no documented case of chia seeds themselves causing bleeding on warfarin, DOACs, aspirin, or antiplatelet drugs, and human studies of dietary omega-3 do not show added bleeding. The anticoagulant caution often cited comes from a different plant (danshen root), not chia.
warfarin + garlic
Concentrated garlic supplements may add to warfarin's blood-thinning effect, mainly through a mild antiplatelet action, though the clinical evidence for important bleeding is weak.