The five coagulation tests are indicators to check whether the body’s blood clotting function is normal. The five coagulation tests include: 1) prothrombin time, 2) partially activated prothrombin time, 3) prothrombin time ratio, 4) international normalized index, and 5) fibrinogen. The five tests of coagulation can make a clear diagnosis of whether the human coagulation function is normal. Coagulation tests are often used clinically for the differential diagnosis of bleeding disorders, for example, patients with large petechiae on the mucous membrane of the skin generally require coagulation tests to see if the skin petechiae are caused by coagulation disorders. Coagulation tests are usually done before surgery to see if the patient’s coagulation function is normal. If the coagulation function is not normal, bleeding will easily occur during or after surgery, and the coagulation function must be corrected before surgery can be given to ensure the safety of surgery.