• The "K" is derived from the German word "koagulation." •Coagulation refers to the process of blood clot formation. •Prothrombin (clotting factor II), if combined with Calcium ( factor IV) –helps produce the clotting effect. -also known as phytonadione • Functions: 1.) Is a cofactor in the synthesis of blood clotting factors, including prothrombin. 2.) Protein formation in bone, kidney, and plasma also depends on the actions of Vitamin K. • AI for Vitamin K: 120 mcg for men and 90 mcg for women. Toxicity: none