Can you take Vitamin K antagonists with Vitamin K2 (Menaquinone)?
This is general information, not medical advice. Supplements can interact with medicines and health conditions. Always check with your doctor or pharmacist before starting or changing supplements.
What the evidence says
Warfarin and other vitamin K antagonists work by blocking your body's use of vitamin K to make clotting factors. Taking a vitamin K2 supplement directly opposes that mechanism: a study of people on long-term warfarin found that every extra 100 mcg/day of dietary vitamin K lowered INR by about 0.2 on average, meaning added vitamin K measurably weakens and destabilises anticoagulant control. Because supplement doses (90-200+ mcg/day for MK-7, 1000+ mcg/day for MK-4) are large and variable compared with typical dietary intake, and because starting or stopping them can swing INR outside the safe range, do not start, stop, or change vitamin K2 supplementation while on a vitamin K antagonist without your prescriber's involvement and close INR monitoring.
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We check against a limited set of medications. Absence of a warning here is not evidence of safety. Always confirm with your pharmacist.