bleeding
28 interactions related to bleeding
warfarin + dong quai
Dong quai (Angelica sinensis) contains coumarin derivatives (ferulic acid, osthole) and has documented antiplatelet activity. A widely cited case report (Page & Lawrence, Pharmacotherapy 1999, PMID 10417036) described a woman whose INR rose to 4.9 within four weeks of adding dong quai 565 mg once to twice daily to stable warfarin.
apixaban + fish oil
Apixaban is a direct factor Xa inhibitor that increases bleeding risk on its own. Omega-3 fatty acids in fish oil reduce platelet aggregation in a dose-dependent way; a 2024 JAHA systematic review of 120,643 patients found omega-3 doses of approximately 3 g/day or less of EPA+DHA did not significantly raise bleeding risk, while higher doses (notably high-purity EPA in cardiovascular trials) showed a small absolute increase in bleeding events.
warfarin + danshen
Danshen (Salvia miltiorrhiza), widely used in traditional Chinese medicine for cardiovascular indications, has both pharmacokinetic (decreased clearance of R- and S-warfarin) and pharmacodynamic (antiplatelet, antithrombotic) interactions with warfarin. Multiple published case reports describe massive over-anticoagulation with INRs above 8 and serious bleeds including haemothorax.
warfarin + feverfew
Feverfew (Tanacetum parthenium) inhibits platelet aggregation in vitro via its parthenolide sesquiterpene lactones. There are no robust human case reports of bleeding with warfarin specifically, but standard herbal-interaction references (StatPearls, Australian Prescriber) recommend avoidance based on the pharmacologic plausibility of additive bleeding risk.
aspirin + ginkgo
Ginkgo biloba can inhibit platelet-activating factor (PAF) and platelet aggregation, which can add to aspirin's irreversible inhibition of cyclooxygenase-1 and thromboxane A2. The combination may modestly increase minor bleeding events, with case reports of more serious bleeds in vulnerable patients.
rivaroxaban + fish oil
Omega-3 fatty acids in fish oil have mild antiplatelet and anticoagulant effects, reducing thromboxane A2 and prolonging bleeding time. Combined with rivaroxaban's Factor Xa inhibition, this can additively increase bleeding risk, particularly at fish oil doses above 3 g per day.
rivaroxaban + ginkgo
Ginkgo biloba has antiplatelet properties and may theoretically add to the bleeding risk of rivaroxaban, although a controlled pharmacokinetic study with EGb 761 found no change in rivaroxaban plasma levels or anti-Factor Xa activity. The risk is primarily additive rather than pharmacokinetic.
aspirin + fish oil
Omega-3 fatty acids in fish oil reduce platelet aggregation and prolong bleeding time slightly, theoretically adding to aspirin's antiplatelet effect. Clinical trials, however, consistently show no clinically significant increase in major bleeding even with high-dose fish oil added to aspirin.
alcohol + warfarin
Alcohol affects warfarin in two opposing ways: acute heavy drinking inhibits hepatic CYP2C9 metabolism of warfarin, raising INR and bleeding risk, while chronic heavy drinking induces enzymes that lower INR and increase clot risk. Alcohol also damages the liver and platelets, compounding bleeding hazards.
warfarin + ginger
Ginger inhibits thromboxane synthase and reduces platelet aggregation; case reports describe elevated INR after addition of oral ginger to stable warfarin therapy. A 2019 case report (Rubin et al., Case Reports in Medicine) and the Tan 2021 BJCP systematic review document the signal, though controlled trials in healthy volunteers have been mixed.
warfarin + ginkgo
Ginkgo biloba inhibits platelet-activating factor and can prolong bleeding time, adding an antiplatelet effect on top of warfarin's vitamin-K-antagonist anticoagulation. A 2025 PLOS One analysis of 2,647 prescriptions found ginkgo co-prescription was associated with a significantly higher rate of bleeding adverse events (hazard ratio ~1.38) and abnormal coagulation profiles.
warfarin + turmeric
Curcumin, the main active in turmeric, has antiplatelet activity and may also inhibit CYP2C9 metabolism of warfarin, raising warfarin levels. New Zealand Medsafe issued an alert in 2018 after a patient's INR rose above 10 within weeks of starting a turmeric/curcumin product on previously stable warfarin therapy.
clopidogrel + ginkgo
Ginkgo biloba inhibits platelet-activating factor and may add to clopidogrel's blockade of the platelet P2Y12 ADP receptor. While a healthy-volunteer study did not detect additive platelet inhibition, observational and case-report data link the combination to increased bleeding, including intracranial hemorrhage.
matcha + warfarin
Matcha is powdered whole green tea leaf, so each serving delivers far more vitamin K than a normal brewed cup. Vitamin K is the cofactor warfarin antagonises, so large or fluctuating matcha intake can lower INR and reduce the anticoagulant effect, similar to the documented green tea-warfarin case report.
cranberry + warfarin
Cranberry juice contains flavonoids that may inhibit CYP2C9, the primary enzyme that metabolizes the active S-enantiomer of warfarin. Multiple case reports describe elevated INR and major bleeding (including fatal hemorrhage) in patients who drank cranberry juice while stably anticoagulated, though randomized trials with smaller doses have not consistently reproduced the effect.
green tea + warfarin
Green tea leaves contain vitamin K, which is a cofactor for hepatic synthesis of the clotting factors that warfarin inhibits. Large or fluctuating intake of green tea can lower INR and reduce the anticoagulant effect of warfarin, as documented in a published case report.
cayenne + warfarin
Capsaicin, the active constituent in cayenne (Capsicum), has been reported to potentiate the anticoagulant effect of warfarin, theoretically through additive effects on platelet aggregation and possible enhancement of warfarin absorption or activity, increasing bleeding risk.
cinnamon + warfarin
Cassia cinnamon contains coumarin, a natural compound with anticoagulant activity that may potentiate warfarin and increase bleeding risk. Case reports describe elevated INR and bleeding when cinnamon supplements were added to stable warfarin therapy.
fenugreek + warfarin
Fenugreek (Trigonella foenum-graecum) contains coumarin-related compounds and has documented in vitro anticoagulant activity. A published case report describes elevated INR when boldo-fenugreek was added to stable warfarin therapy, with INR normalizing on discontinuation and rising again on rechallenge.
turmeric tea + warfarin
Curcumin, the principal active compound in turmeric, has antiplatelet and anticoagulant activity in vitro (inhibiting thrombin and factor Xa) and inhibits CYP enzymes involved in warfarin metabolism. Case reports describe INR rising above 10 within weeks of starting turmeric in patients on stable warfarin.
chamomile tea + warfarin
Chamomile contains coumarin-like compounds that may potentiate warfarin's anticoagulant effect. A published case report described a 70-year-old woman on stable warfarin who developed retroperitoneal hemorrhage with an INR of 7.9 after using chamomile tea and lotion for upper respiratory symptoms.
flaxseed + warfarin
Flaxseed contains alpha-linolenic acid that can mildly reduce platelet aggregation and may add to warfarin's bleeding risk, particularly at high supplemental doses. Flaxseed is also very high in soluble fiber, which can bind warfarin in the gut and erratically reduce its absorption.
cocoa + warfarin
Cocoa flavanols inhibit platelet adhesion and aggregation and can mildly prolong bleeding time. Layered on top of warfarin's anticoagulant effect, large or fluctuating intakes of cocoa can increase bleeding risk without necessarily moving the INR.
clopidogrel + garlic
Garlic supplements, especially aged garlic extract, inhibit platelet aggregation through reduced thromboxane B2 and altered platelet membrane function. Combined with clopidogrel's P2Y12 blockade, this adds antiplatelet effect and can increase bleeding risk, particularly with concentrated supplement doses.
fluconazole + warfarin
Fluconazole inhibits CYP2C9 and CYP3A4, the enzymes that clear warfarin, and can rapidly raise INR by 50 to 100 percent or more within two to three days of starting, with documented cases of major bleeding and death.
acai + warfarin
Acai berries contain polyphenols, salicylate-like compounds, and unsaturated fatty acids that may have mild antiplatelet activity, but there are no published case reports of clinically significant INR changes. The theoretical concern is additive bleeding risk at high doses or with concentrated extracts, not enzymatic CYP interference.
chia seeds + blood thinners
Chia seeds are high in plant-form omega-3 (alpha-linolenic acid) and soluble fiber, both of which can mildly reduce platelet aggregation and theoretically add to the bleeding risk of warfarin, DOACs, aspirin, and antiplatelet drugs. The Drugs.com chia monograph explicitly flags caution with anticoagulants based on case reports for related species.
warfarin + garlic
Concentrated garlic supplements have antiplatelet activity (mainly via ajoene and allicin) and have been associated with elevated INR and bleeding when added to warfarin in case reports and herbal-interaction reviews. The Vaes & Chyka review in Annals of Pharmacotherapy classified garlic as a potential potentiator of warfarin via additive antithrombotic effect.