High-dose vitamin E increases warfarin bleeding risk
Vitamin E (>400 IU/day) inhibits vitamin K-dependent clotting and enhances warfarin's effect. Can increase INR and bleeding risk. Mixed tocopherols may have stronger effect than alpha alone.
Avoid high-dose vitamin E on warfarin. If needed, use under 200 IU/day with monitoring.
Monitor INR closely if combining
High-dose vitamin E increases warfarin bleeding risk. Avoid high-dose vitamin E on warfarin. If needed, use under 200 IU/day with monitoring.
Monitor INR closely if combining
This interaction is rated “Warning” by Formulate. Vitamin E (>400 IU/day) inhibits vitamin K-dependent clotting and enhances warfarin's effect. Can increase INR and bleeding risk. Mixed tocopherols may have stronger effect than alpha alone.
Studies from our registry that mention vitamin e 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 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.
Mentions vitamin e · 2012
Silybin combined with phosphatidylcholine and vitamin E in patients with nonalcoholic fatty liver disease
Loguercio C, Andreone P, Brisc C, et al. · Free Radical Biology and Medicine
12-month RCT (n=138) in NAFLD found a silybin-phosphatidylcholine-vitamin E complex reduced insulin resistance and liver enzymes vs placebo, supporting phytosome forms of silymarin for NAFLD.
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
Garlic supplements increase bleeding risk
Dong quai contains natural coumarins and has potentiated warfarin in a published case, raising bleeding risk.
High-dose vitamin E may interfere with vitamin K
Ginger may enhance anticoagulant effect
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Medical disclaimer. This page is for educational purposes only and does not replace advice from a qualified healthcare provider.
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