NutriStack
Vitamin K2 and Warfarin, a conflict.
Vitamin K2 directly opposes warfarin's mechanism of action. Warfarin works by inhibiting vitamin K-dependent clotting factor synthesis, so supplemental vitamin K2 can restore clotting factor production and significantly reduce warfarin's anticoagulant effect. Even small, consistent doses of K2 can shift INR values unpredictably.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- Vitamin K2 and Warfarin
- Pair type
- Conflict
- Evidence (highest tier)
- Strong
- Source citations
- 6 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 directly opposes warfarin's mechanism of action. Warfarin works by inhibiting vitamin K-dependent clotting factor synthesis, so supplemental vitamin K2 can restore clotting factor production and significantly reduce warfarin's anticoagulant effect. Even small, consistent doses of K2 can shift INR values unpredictably.
Mechanism. Warfarin inhibits vitamin K epoxide reductase (VKORC1), preventing recycling of vitamin K needed for gamma-carboxylation of clotting factors II, VII, IX, and X. Exogenous vitamin K2 bypasses this inhibition by providing substrate directly.
Recommendation. Avoid vitamin K2 supplementation while on warfarin unless directed and closely monitored by your prescriber. If K2 is deemed necessary, maintain a very consistent daily dose and monitor INR frequently.
Sources (6)
- Booth SL, Centurelli MA. Vitamin K: a practical guide to the dietary management of patients on warfarin. Nutr Rev. 1999;57(9):288-296. PMID 10568341
- Shearer MJ, Newman P. Recent trends in the metabolism and cell biology of vitamin K with special reference to vitamin K cycling and MK-4 biosynthesis. J Lipid Res. 2014;55(3):345-362. PMID 24489112
- Wang M, Zeraatkar D, Obeda M, Lee M et al.. Drug-drug interactions with warfarin: A systematic review and meta-analysis. British Journal of Clinical Pharmacology. 2021. PMID 33769581
- Ma ML, Ma ZJ, He YL et al.. Efficacy of vitamin K2 in the prevention and treatment of postmenopausal osteoporosis: A systematic review and meta-analysis of randomized controlled trials. Frontiers in Public Health. 2022. PMID 36033779
- Kuang X, Liu C, Guo X, Li K, Deng Q, Li D. The combination effect of vitamin K and vitamin D on human bone quality: a meta-analysis of randomized controlled trials. Food & Function. 2020. PMID 32219282
- Zhou M, Han S, Zhang W, Wu D. Efficacy and safety of vitamin K2 for postmenopausal women with osteoporosis at a long-term follow-up: meta-analysis and systematic review. Journal of Bone and Mineral Metabolism. 2022. PMID 35711002
Stack Score
How this pair moves the number.
Effect on the composite score
If both Vitamin K2 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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