A prothrombin time ( PT/INR) test measures how fast your blood clots. Healthcare providers often do this test to monitor blood clotting if you’re taking warfarin. Learn about the coagulation profile test that measures how rapidly blood clots and its applications in diagnosing and monitoring bleeding and clotting disorders. Find out the normal range, test methods, and clinical significance of PT , INR , and APTT test results. PT INR normal range explained with details on prothrombin time levels. Learn how these values affect blood clotting and overall health. Prothrombin time and INR : Understand the test which measures blood clotting efficiency. Learn results interpretation and more today!