Coagulation is the blood’s ability to clot in order to stop bleeding. Coagulation testing gives important information about the balance between elevated bleeding risk on one side and increased risk of dangerous thrombosis on the other side. Several techniques are used for coagulation testing, providing an assessment of coagulation function, for example in patients with liver disease, thrombophilia, and hemophilia (abnormal blood clotting). Also, people who have to take medications that affect blood clotting need to be monitored with coagulation tests. These tests comprise the measurement of prothrombin time (PT), partial thromboplastin time (PTT), and the international normalized ratio (INR).