Dr. Kumar’s Take:
This study highlights an important warning: even small doses of vitamin K2 (as low as 10 mcg daily) can interfere with the stability of Vitamin K antagonizing blood thinners like Coumadin. While K2 is often promoted for bone and heart health, patients on vitamin K antagonists (like warfarin or acenocoumarol) should avoid taking MK-7 supplements without medical guidance. The impact on INR was significant in many participants, even at low doses.
If you’re on a blood thinner, don’t assume low-dose supplements are safe—talk to your doctor first.
Key Takeaways:
✔ MK-7 supplements reduced the effectiveness of blood thinners, even at 10–20 mcg per day.
✔ INR levels dropped in up to 60% of users at 20 mcg, increasing blood clotting risk.
✔ Effects were stronger than with vitamin K1 and persisted even at low doses.
✔ MK-7 reversed liver-based anticoagulation before affecting bone or vascular markers.
Actionable tip:
If you’re taking a vitamin K antagonist like warfarin or acenocoumarol, avoid any supplement containing vitamin K2 (MK-7) unless specifically advised by your healthcare provider.
Brief Summary:
This 2013 study evaluated how low doses of MK-7 (vitamin K2) affect blood thinner stability in healthy adults. Over six weeks, participants took 10, 20, and 45 mcg daily while continuing their acenocoumarol regimen. Researchers found that MK-7, even at the lowest doses, could significantly reduce the INR in many subjects—potentially increasing clotting risk. MK-7’s effect was stronger and longer-lasting than vitamin K1, suggesting patients on blood thinners should avoid even small amounts.
Study Design:
- Type: Open-label, dose-escalation study
- Participants: 18 healthy adults anticoagulated with acenocoumarol
- Duration: 10 weeks (4 weeks stabilization + 6 weeks MK-7)
- Intervention: Daily MK-7 at 10 mcg (weeks 5–6), 20 mcg (weeks 7–8), and 45 mcg (weeks 9–10)
- Primary Outcome: Changes in INR
- Secondary Outcomes: Thrombin generation, uncarboxylated factor II (ucFII), osteocalcin, matrix Gla-protein
Results:
- INR dropped significantly in many subjects at 10 and 20 mcg of MK-7.
- 45 mcg MK-7 reduced INR by 37% on average.
- Thrombin generation (clotting potential) increased as MK-7 doses rose.
- MK-7 affected liver-based clotting markers but not bone/vascular vitamin K proteins.
How MK-7 Interferes with Blood Thinners
MK-7 supports vitamin K-dependent clotting proteins by helping them activate properly. But blood thinners like warfarin or acenocoumarol work by blocking that same activation. Adding MK-7 effectively “undoes” some of the blood thinner’s action—even in tiny amounts. This makes clotting more likely and the blood thinner less predictable.
Related Studies and Research
Assesses MK-7’s influence on anticoagulation therapy stability and potential dose-response effects. – Evaluates MK-7’s impact on INR variability in patients on vitamin K antagonists.
Explores how vitamin K2 may influence heart disease outcomes, focusing on arterial stiffness and calcification. – Foundational summary of K2’s cardiovascular benefits.
Reviews the connection between vitamin K2 and reduced arterial calcification, including clinical data. – Chronicles clinical trial data on calcification reduction.
Meta-analysis showing vitamin K’s effect on arterial calcification progression in different populations. – Aggregates outcomes on calcification changes with K supplementation.
Examines how warfarin use is linked with increased arterial calcification risk due to vitamin K inhibition. – Details warfarin’s unintended calcification effects.
Frequently Asked Questions
How much MK-7 caused problems in the study?
Even just 10 mcg per day (much lower than the 45–200 mcg commonly sold) affected INR levels in almost half the participants.
Is MK-7 more dangerous than vitamin K1 for people on blood thinners?
Yes. MK-7 is more potent and stays in the body longer than vitamin K1, making it more disruptive to blood thinner stability.
Can people on blood thinners take K2 for their bones?
Not without careful supervision. Even low doses affect INR. If K2 is needed, doctors may adjust anticoagulant doses, but self-supplementation is risky.
Is this relevant for warfarin, or only acenocoumarol?
Although the study used acenocoumarol, similar effects are expected with warfarin, since both block the same enzyme (VKOR). Caution applies to all VKAs.
Conclusion
This study provides strong evidence that vitamin K2 (MK-7) supplements—even in very small amounts—can interfere with common blood thinners like acenocoumarol or warfarin. These findings are especially important as MK-7 grows in popularity for heart and bone health. Patients on VKAs should avoid K2 supplements unless carefully managed by their healthcare provider.