NutriStack
Vitamin K2 MK-4 and Warfarin, a conflict.
Vitamin K2 in the MK-4 (menatetrenone) form opposes warfarin in the same way as K1 and K2 MK-7: it restores production of vitamin K-dependent clotting factors. MK-4 is used clinically (often intravenously) to reverse warfarin, which is direct evidence that supplemental MK-4 will reduce warfarin's effect. Even modest oral doses can blunt anticoagulation.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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What the row says.
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At a glance
- Substances
- Vitamin K2 MK-4 and Warfarin
- Pair type
- Conflict
- Evidence (highest tier)
- Strong
- Source citations
- 2 sources
- Stack Score effect
- −10 to your Stack Score (per scored conflict row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Conflict · Strong evidence
Conflict
What is happening. Vitamin K2 in the MK-4 (menatetrenone) form opposes warfarin in the same way as K1 and K2 MK-7: it restores production of vitamin K-dependent clotting factors. MK-4 is used clinically (often intravenously) to reverse warfarin, which is direct evidence that supplemental MK-4 will reduce warfarin's effect. Even modest oral doses can blunt anticoagulation.
Mechanism. MK-4 supplies a vitamin K substrate that is gamma-carboxylated by enzymes downstream of VKORC1, restoring functional clotting factors II, VII, IX, and X despite warfarin's inhibition of vitamin K recycling.
Recommendation. Avoid vitamin K2 MK-4 supplements while taking warfarin unless your prescriber has explicitly approved it. If you cannot avoid it, keep the dose and timing identical every day and ask for an INR check within 1-2 weeks of starting.
Sources (2)
- Holbrook AM, Pereira JA, Labiris R, et al. Systematic overview of warfarin and its drug and food interactions. Arch Intern Med. 2005;165(10):1095-106. PMID 15911722
- Tan CSS, Lee SWH. Warfarin and food, herbal or dietary supplement interactions: A systematic review. Br J Clin Pharmacol. 2021;87(2):352-374. PMID 32478963
Stack Score
How this pair moves the number.
Effect on the composite score
If both Vitamin K2 MK-4 and Warfarin are in the same stack, this pair applies −10 to your Stack Score (per scored conflict row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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