A double-blind, placebo-controlled study, appearing in the journal Blood (15 March 2007, Vol. 109, No. 6, pp. 2419-2423.), found that vitamin K supplementation may improve the stability of patients who have unstable control of anticoagulation while on warfarin. Seventy patients taking warfarin, with unstable anticoagulation control were randomly given either a placebo or 150 mcg. of vitamin K for a period of six months. Anticoagulation control improved in 34 of the subjects receiving the supplement, with 19  of  those fulfilling the study criteria for having stable control of anticoagulation. Only seven patients in the control group fulfilled the study criteria for stable control of anticoagulation.