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Supplement × Prescription·Evidence index

Vitamin E and Warfarin: what the research found

PubMed indexes 8 records that name Vitamin E and Warfarin together, either in the title or in an interaction, co-administration, or pharmacokinetic context. The key findings come first, in the authors’ own words, followed by every study with its design and PubMed link.

A summary of published research, not medical advice. A pharmacist can check any combination against your full list of medicines and supplements.

Key findings

What the studies concluded.

Reviews and human studies first. Each quote is the authors’ own conclusion about their study, not a NutriStack assessment, and a single study is not a consensus.

“Evidence of low-strength indicates benefits of omega-3 fatty acids (plus statin, or calcium channel blockers and antiplatelets) and garlic (plus nitrates or warfarin) on triglycerides and HDL-C, respectively. Safety concerns, however, persist.”

Kanji et al. · 2012 · Review or meta-analysis · details

“To clarify whether vitamin E enhances the pharmacologic effect of warfarin, we completed a double-blind clinical trial in which 21 subjects taking chronic warfarin therapy were randomized to receive either vitamin E or placebo. None of the subjects who received vitamin E had a significant change in the international normalized ratio, and thus it appears that vitamin E can safely be given to patients who require…”

Kim et al. · 1996 · Human study · details

“Factor II antigen as determined by electroimmunoassay in humans and factor II coagulant activity as measured using Echis venom in animals were unchanged and no different from untreated controls. The data suggest that vitamin E acts at the vitamin K-carboxylase step of carboxylation of precursor prothrombin and not in the synthesis of the precursor protein.”

The research

8 studies naming Vitamin E and Warfarin.

Strongest relevance first: papers naming both substances in the title, then human trials and systematic reviews.

Effect of vitamin E on the anticoagulant response to warfarin.

The American journal of cardiology · 1996 · PMID 8629604

Clinical TrialRandomized Controlled Trial

“To clarify whether vitamin E enhances the pharmacologic effect of warfarin, we completed a double-blind clinical trial in which 21 subjects taking chronic warfarin therapy were randomized to receive either vitamin E or placebo. None of the subjects who received vitamin E had a significant change in the international normalized ratio, and thus it appears that vitamin E can safely be given to patients who require chronic warfarin therapy.”

Kim et al. · From the abstract

Names both Vitamin E and Warfarin in its title.

Effect of vitamin E on prothrombin levels in warfarin-induced vitamin K deficiency.

The American journal of clinical nutrition · 1981 · PMID 7282596

Clinical TrialRandomized Controlled Trial

“These data suggest that vitamin E acts at the step mediated by vitamin K and not in the synthesis of the factor II precursor. Although the administration of high doses of vitamin E in animals, and possibly humans, with vitamin K deficiency potentiates the vitamin K deficiency, this effect is not clinically obvious with 400 IU/day or less.”

Corrigan et al. · From the abstract

Names both Vitamin E and Warfarin in its title.

Ask the doctor. I am 95 years old and recently began treatment for early macular degeneration in one eye. My retinologist said that PreserVision might help protect the other eye. But she cautioned that it contains a large dose of vitamin E, which could cause a bleeding problem with the Coumadin I take because of a mechanical aortic valve. What would you suggest?

Harvard heart letter : from Harvard Medical School · 2010 · PMID 20590010

Human subjects

Names both Vitamin E and Warfarin in its title.

The effect of vitamin E on warfarin-induced vitamin K deficiency.

Annals of the New York Academy of Sciences · 1982 · PMID 6959563

Human subjects

“Factor II antigen as determined by electroimmunoassay in humans and factor II coagulant activity as measured using Echis venom in animals were unchanged and no different from untreated controls. The data suggest that vitamin E acts at the vitamin K-carboxylase step of carboxylation of precursor prothrombin and not in the synthesis of the precursor protein.”

Corrigan · From the abstract

Names both Vitamin E and Warfarin in its title.

Interactions of commonly used dietary supplements with cardiovascular drugs: a systematic review.

Systematic reviews · 2012 · PMID 22651380

Systematic ReviewHuman subjects

“Evidence of low-strength indicates benefits of omega-3 fatty acids (plus statin, or calcium channel blockers and antiplatelets) and garlic (plus nitrates or warfarin) on triglycerides and HDL-C, respectively. Safety concerns, however, persist.”

Kanji et al. · Authors' conclusion

Names Vitamin E and Warfarin together in an interaction, co-administration, or pharmacokinetic context.

Effective and safe modification of multiple atherosclerotic risk factors in patients with peripheral arterial disease.

American heart journal · 2000 · PMID 11054628

Clinical TrialRandomized Controlled Trial

“ADMIT demonstrates that it is both feasible and safe to modify multiple atherosclerotic disease risk factors effectively with intensive combination therapy in patients with PAD.”

Garg et al. · Authors' conclusion

Names Vitamin E and Warfarin together in an interaction, co-administration, or pharmacokinetic context.

Limitations

What this evidence cannot tell you.

Search-based evidence indexes have real limits, and it is worth being explicit about them:

How to read this page

A literature summary, not guidance.

NutriStack

Track what you actually take.

NutriStack is a free iPhone app for organising a supplement routine: what you take, when, and what the published record says about it. Its exploratory interaction checker covers Vitamin E, Warfarin, and several hundred other substances.

Log your routine, get reminders at the times you choose, and scan a label to add a product. The checker is a research and organisation tool, not a clinical decision aid.

NutriStack is an informational and organizational tool, not a medical service, and not a substitute for professional advice. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or medication.