The Full form of PT is Prothrombin Time. PT is a blood test that measures the time it takes for plasma (the liquid portion) of your blood to clot. A related blood test is Partial Thromboplastin Time (PTT). A Prothrombin Time is a test used to help detect and diagnose a bleeding disorder or excessive clotting disorder; the International Normalized Ratio (INR) is calculated from a PT result and is used to monitor how well the blood-thinning medication is working to prevent blood clots. The PT is a test that helps evaluate a body’s ability to appropriately form blood clots. A PT measures the number of seconds it takes for a clot to form in your sample of blood after reagents (substances) are added. The PT is often performed along with a Partial Thromboplastin Time (PTT) and together they assess the amount and function of proteins called coagulation factors that are an important part of proper blood clot formation. The Food and Drug Administration (FDA) has approved several home INR and PT testing systems. However, home testing is usually done in the context of a home-based coagulation management program that involves patient training and defined response and management protocols.