Garlic supplements increase bleeding risk
Garlic inhibits platelet aggregation through multiple mechanisms including inhibition of thromboxane synthesis. Combined with warfarin, significantly increases bleeding risk. Dietary garlic in normal amounts is generally safe.
Avoid garlic supplements on warfarin. Inform doctor. Culinary use is acceptable.
Discontinue garlic supplements 7-10 days before surgery
Garlic supplements increase bleeding risk. Avoid garlic supplements on warfarin. Inform doctor. Culinary use is acceptable.
Discontinue garlic supplements 7-10 days before surgery
This interaction is rated “Warning” by Formulate. Garlic inhibits platelet aggregation through multiple mechanisms including inhibition of thromboxane synthesis. Combined with warfarin, significantly increases bleeding risk. Dietary garlic in normal amounts is generally safe.
Studies from our registry that mention garlic or warfarin. Each links to the primary source and the other Formulate pages citing it.
Mentions warfarin · 2025
Impact of Ginkgo biloba drug interactions on bleeding risk and coagulation profiles
Primary literature · Observational study
Ginkgo + aspirin: bleeding risk OR 1.12 (95% CI 1.07-1.18, p<0.001); abnormal coagulation OR 1.48 (95% CI 1.32-1.66, p<0.001). Ginkgo + clopidogrel: bleeding risk OR 1.10 (95% CI 1.05-1.15, p<0.001); abnormal coagulation OR 1.58 (95% CI 1.40-1.77, p<0.001). Ginkgo + warfarin: NO statistically significant correlation with bleeding or coagulation.
Mentions warfarin · 2016
Interaction Between Dietary Vitamin K Intake and Anticoagulation by Vitamin K Antagonists: Is It Really True? A Systematic Review
Violi et al. · Medicine (Baltimore)
Conflicting evidence on whether dietary vitamin K intake affects warfarin response. Some studies show inverse correlation between vitamin K intake and INR changes. Others suggest a minimum vitamin K intake is REQUIRED for stable anticoagulation. Conclusion: available evidence does NOT support the old advice to restrict dietary vitamin K when starting warfarin. Consistency of intake matters more than absolute level.
Mentions warfarin · 2015
Ginkgo and Warfarin Interaction in a Large Veterans Administration Population
Millery et al. · AMIA Annu Symp Proc
Hazard ratio for bleeding adverse event with concurrent ginkgo + warfarin: 1.38 (95% CI 1.20-1.58, p<0.001).
Mentions warfarin · 2015
Interaction between warfarin and Chinese herbal medicines
Lin et al. · Stat Med
Dong quai listed among Chinese herbal medicines with documented warfarin potentiation via PD mechanism. Recommends caution when combining.
Mentions garlic · 2015
Phosphatidylserine and the human brain
Glade MJ, Smith K · Nutrition
Reviews mechanisms (neuronal membrane integrity, acetylcholine release, HPA-axis modulation) and clinical evidence for PS in age-related cognitive decline and exercise-induced cortisol attenuation.
Mentions warfarin · 2014
Warfarin Interactions with Medicinal Herbs
Primary literature · Systematic review
Dong quai contains natural coumarin derivatives (ferulic acid, osthole) with documented antithrombotic and platelet-inhibitory effects. Animal steady-state studies show dong quai significantly increased prothrombin time WITHOUT affecting warfarin concentration - suggesting pharmacodynamic (not pharmacokinetic) interaction. Recommends informing patients of the potential hazard.
Other interactions to know
K2 also reverses warfarin's effect
Salvia miltiorrhiza potentiates warfarin
Vitamin K directly antagonizes warfarin. Consistency of intake, not avoidance, is the right clinical approach.
Fish oil may increase bleeding risk with warfarin
High-dose vitamin E increases warfarin bleeding risk
Dong quai contains natural coumarins and has potentiated warfarin in a published case, raising bleeding risk.
Ginger may enhance anticoagulant effect
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