The thrombin time(TT) test may be done to investigate a possible bleeding disorder or inappropriate blood clot formation. Mostly done to evaluate the function and level of fibrinogen. This test is very sensitive to the anticoagulant heparin. A thrombin time test is ordered by itself or along with some of other tests when a person is experiencing bleeding or clotting, experiences continuous miscarriages, or has prolonged disturbed results on the primary coagulation tests like prothrombin time (PT) or partial thromboplastin time (PTT). This test is also done for heparin contamination or when a person is undergoing heparin therapy.