Warfarin is an anticoagulant, or anti-clotting medication, is used for the prevention of future blood clots in those who are at risk for clot formation. Because warfarin interacts with many foods and commonly-prescribed medications and its metabolism varies from person to person, it can be difficult to determine the optimal dosage and over-dosing can lead to serious bleeding events. Vitamin K is essential for blood clotting, so it might seem that vitamin K supplementation could reduce the risk of bleeding in patients on warfarin.

Unfortunately, according to an article in a recent issue of Annals of Internal Medicine, low-dose oral vitamin K does not reduce bleeding in patients who have been over-anticoagulated on warfarin . Canadian researchers studied over 700 patients from 14 anticoagulant therapy clinics, half of whom were assigned to vitamin K therapy and half of whom were assigned to placebo treatment. The researchers found that there was no difference in the rate of bleeding complications among the two groups.

Based on their findings, the researchers concluded that withholding warfarin treatment might be the best way to manage bleeding risk in patients who are over-dosed with warfarin.

Source

Ann Intern Med. 2009;150:293-300.