Drug interactions
Vitamin k1 + Warfarin
Severity: Major
Vitamin k1 and Warfarin: major interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Vitamin K1 directly antagonizes warfarin and reduces INR, leading to loss of anticoagulation. This is used therapeutically for reversal but can cause unintended resistance with supplements.
What this interaction means in plain words
Vitamin k1 and Warfarin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Vitamin k1 belongs to Cardiovascular; Warfarin belongs to Cardiovascular.
Why it happens
Vitamin K1 restores synthesis of clotting factors II, VII, IX and X, opposing warfarin's inhibition of VKOR.
What to do
Keep vitamin K intake consistent and monitor INR whenever dosing changes; when used for reversal, titrate dose to INR and bleeding status.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Warfarin
- Defibrotide + Warfarin Contraindicated
- Ketorolac + Warfarin Contraindicated
- Abciximab + Warfarin Major
- Acetylsalicylic acid + Warfarin Major
- Adagrasib + Warfarin Major
- Amiodarone + Warfarin Major
Other interactions of Vitamin k1
- Cholestyramine + Vitamin k1 Moderate
- Colestipol + Vitamin k1 Moderate
- Ketorolac intranasal + Vitamin k1 Moderate
- Mineral oil + Vitamin k1 Moderate
- Orlistat + Vitamin k1 Moderate
- Aescin + Vitamin k1 Minor
Frequently asked questions
Can I take Vitamin k1 with Warfarin?
MediHelp rates the interaction as major. Vitamin k1 and Warfarin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Vitamin K1 directly antagonizes warfarin and reduces INR, leading to loss of anticoagulation. This is used therapeutically for reversal but can cause unintended resistance with supplements.
How serious is the interaction between Vitamin k1 and Warfarin?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Keep vitamin K intake consistent and monitor INR whenever dosing changes; when used for reversal, titrate dose to INR and bleeding status.
What other medicines interact with Warfarin?
MediHelp also lists interactions of Warfarin with, for example, Defibrotide, Ketorolac, Abciximab. The full list is on the Warfarin page.
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