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Vitamin K × Anticoagulants

CRITICAL INTERACTION — Well-Established Evidence

⚠️ Mechanism

Vitamin K antagonizes the effect of all vitamin K antagonist anticoagulants (warfarin, acenocoumarol, phenprocoumon).

📋 Effect

Reduced anticoagulant effect; increased thrombosis risk

💊 Management

Avoid vitamin K supplements. Maintain consistent dietary vitamin K intake.

Plain Language Summary

This combination is dangerous. Taking Vitamin K supplements can interfere with how blood-thinning medications work, which increases the risk of developing blood clots.

Source

FDA warfarin labeling; Holbrook AM et al. Ann Intern Med 2005

Supporting Research

Antiplatelet and anticoagulant agents for secondary prevention of stroke and other thromboembolic events in people with antiphospholipid syndrome PMID:28968483 DOI:10.1002/14651858.CD012169.pub2 2017
Anticoagulants (extended duration) for prevention of venous thromboembolism following total hip or knee replacement or hip fracture repair PMID:27027384 DOI:10.1002/14651858.CD004179.pub2 2016
Antiplatelet and anticoagulant agents for secondary prevention of stroke and other thromboembolic events in people with antiphospholipid syndrome PMID:33045766 DOI:10.1002/14651858.CD012169.pub3 2020
Direct factor Xa inhibitors versus low molecular weight heparins or vitamin K antagonists for prevention of venous thromboembolism in elective primary hip or knee replacement or hip fracture repair PMID:39868562 DOI:10.1002/14651858.CD011762.pub2 2025
Factor Xa inhibitors versus vitamin K antagonists for preventing cerebral or systemic embolism in patients with atrial fibrillation PMID:29509959 DOI:10.1002/14651858.CD008980.pub3 2018
Antiplatelet agents and anticoagulants for hypertension PMID:35900898 DOI:10.1002/14651858.CD003186.pub4 2022
Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy PMID:22336844 DOI:10.1002/14651858.CD008500.pub2 2012
Factor Xa inhibitors versus vitamin K antagonists for preventing cerebral or systemic embolism in patients with atrial fibrillation PMID:23925867 DOI:10.1002/14651858.CD008980.pub2 2013
Medical Disclaimer: This interaction record is for informational and educational purposes only and does not constitute medical advice. Drug-supplement interactions can be dangerous. Always consult your healthcare provider or pharmacist before combining any supplement with prescription medications. Do not stop or change any medication without professional guidance.