K-oagulation factor

VITAMIN K, like vitamins A, D and E, is a fat-soluble vitamin, which means it is metabolised along with fat in the body and is best taken with meals. But unlike those more familiar substances, not much vitamin K is stored in your body fat. Fortunately, about 80% of the vitamin K you need is synthesised by bacteria that live in your intestinal tract.  

Without vitamin K, your blood would not clot. The process by which this works is complex; basically, vitamin K acts as a catalyst that transforms anti-clotting proteins into clotting proteins when you suffer a cut or wound.