Protein C is one of many natural anticoagulants in blood that helps keep your clotting mechanism in check. An anticoagulant is a substance that prevents blood from clotting. Protein C deficiency means you don’t have enough of this substance (protein C) to protect you from excessive clotting. He named it protein C because it was the third protein ( peak C ) that eluted from a DEAE-Sepharose ion-exchange chromotograph. Seegers was, at the time, searching for vitamin K-dependent coagulation factors undetected by clotting assays, which measure global clotting function. A protein C test measures protein C in your blood; a protein S test measures protein S. Normally, proteins C and S work together to prevent your blood from clotting too much. Protein C is a natural protein produced primarily by the liver, belonging to a group known as anticoagulants. Chemically, it functions as an enzyme that helps control blood clotting by inactivating specific clotting factors. Learn about Protein C and S levels, their role in blood clotting, deficiency causes, symptoms, and testing. Discover diagnosis, treatment, and prevention strategies. This topic review discusses the diagnosis and management of protein C deficiency (inherited and acquired). Separate topic reviews address the appropriate use of thrombophilia testing in various clinical settings: The CRP test measures the level of C-reactive protein in your blood. This protein is produced by your liver, and its level rises when there's inflammation in the body. The normal protein C level in a healthy adult is approximately 65-135 IU/dL. For a healthy term infant, the average value is 40 IU/dL, which will increase as the child ages, to approximately 60. Acquired decreases in protein C occur in patients with liver disease or disseminated intravascular coagulation (DIC) and during warfarin therapy. Diagnosis is based on antigenic and functional plasma assays of protein C. Protein C is a serine protease synthesized by the liver that acts as a potent inhibitor of activated factor V and VIII, and is involved in the activation of fibrinolysis. It is activated by contact with thrombin and thrombomodulin on the surface of endothelial cells.