A double-blind, placebo-controlled study published in Blood (15 March 2007;109(6):2419–2423) found that vitamin K supplementation may help stabilize anticoagulation in patients taking warfarin who have difficulty maintaining consistent INR levels.

The study included 70 patients with unstable anticoagulation control. They were randomly assigned to receive either a placebo or 150 mcg of vitamin K daily for six months.

  • 34 patients in the vitamin K group showed improved anticoagulation stability

  • 19 of those met the study criteria for stable control

  • In contrast, only 7 patients in the placebo group achieved stable control

The authors concluded that small, consistent doses of vitamin K may improve INR stability in certain warfarin users, though therapy must always be supervised by a prescribing physician due to the complex interactions between vitamin K and anticoagulant medications.