Vitamin K acts as a cofactor in the liver's synthesis of coagulation proteins, and a daily intake of 50-100 micrograms is usually sufficient. Coagulants like plasma fractions containing coagulation factors VIII and IX are used to treat deficiencies that cause bleeding disorders. Anticoagulants prevent thrombus formation and embolism by reducing fibrin formation; they include heparin and low molecular weight heparins, warfarin and related oral anticoagulants, and newer direct factor Xa and thrombin inhibitors. Monitoring of anticoagulant levels is important when they are used to treat conditions involving deep vein thrombosis, pulmonary embolism, myocardial infarction and others.