Test Details: Protein S is a natural anticoagulant i.e. it protects blood from clotting too much. If there is reduced level of protein S then there are more chances of blood clotting. Protein S deficiency is mild there is no formation of dangerous blood clot. But certain conditions can increase the risk of clot formation such as pregnancy, surgery, infections and extended period of inactivity. Protein S level are done in case of family history of clotting disorder, unexplained thrombosis, Clot formation at unusual location, age <50 years, history of recurrent miscarriage.