Documented concern based on cited evidence — not a personalized safety check, not medical advice, and not a decision to combine or avoid. That decision belongs with your prescriber.
Significant interaction — talk to your prescriber before combining
Significant documented interaction. Talk to your prescriber before combining these two.
Mechanism and evidence
Vitamin K directly antagonizes warfarin mechanism. Starting or stopping a K supplement shifts INR, and variability itself raises risk on both sides: clotting and bleeding.
Evidence tier: cochrane-rct
The tier names the strongest cited study design. Some anchors studied the supplement on its own, or a related drug in the same class — in those pairs the grade rests on that evidence plus established pharmacology, as agreed with our medical reviewer.
What to discuss with your prescriber
- Do not start or stop a vitamin K supplement on warfarin without your anticoagulation clinic.
- Consistency matters more than more-or-less.