Oral anticoagulants work by inhibiting the functions of vitamin K. Vitamin K1 may interact or interfere with warfarin and other anticoagulants due to its ability to support healthy blood coagulation. One study suggests that supplementation with vitamin K2 (MK-7) as low as 10 μg (lower than the regular retail dose of 45 μg) will significantly affect the anticoagulation sensitivity in some individuals. Therefore, the researchers recommend avoiding MK-7 supplements when vitamin K antagonists are used.

However, studies also have shown that taking vitamin K2 (MK-7), up to 50mcg per day, can more complete activate osteocalcin in patients who are treated with oral anticoagulants without interfering with blood thinners. In other words, taking a small amount of MK-7 can avoid the side effects of these drugs without interfering with their expected benefits.

On the basis of the latest insights, in order to maintain safety, it is recommended that patients who are taking conventional blood thinners should consult their doctor before taking vitamin K2 supplements, as taking more than 50 mcg of vitamin K2 may interfere with their prescription.