Vitamin K is necessary for proper bone growth and blood coagulation. Vitamin K accomplishes this by helping the body transport calcium. Vitamin K is used to treat overdoses of the drug warfarin. Also, doctors prescribe vitamin K to prevent excessive bleeding in people taking warfarin but requiring surgery.

There is some evidence that vitamin K2 (menadione), not vitamin K1 (phylloquinone; phytonadione), may improve a group of blood disorders known as myelodysplastic syndromes (MDS). These syndromes carry a dramatically increased risk of developing acute myeloid leukemia. Comprehensive trials of K2 for MDS are needed to confirm these auspicious early