Vitamin K is a group of vitamins found in certain green vegetables. Vitamins K1 (phytonadione) and K2 (menaquinone) are commonly available as dietary supplements. Vitamin K is an important vitamin that the body needs for blood clotting, bone formation and other important processes. It is found in green leafy vegetables, broccoli and Brussels sprouts. The name vitamin K comes from the German word for “coagulation vitamin”.