Prothrombin time (PT) is a blood test that measures how long it takes blood to clot. A prothrombin time test can be used to check for bleeding problems. PT is also used to check whether medicine to prevent blood clots is working. A PT test may also be called an INR test.
When you get a cut and your blood vessel ruptures, blood platelets collect at the site of the wound. They create a temporary plug to stop the bleeding. In order to produce a strong blood clot, a series of 12 plasma proteins, or coagulation “factors,” act together to make a substance called fibrin, which seals the wound.
PT is measured in seconds. Most of the time, results are given as what is called INR (international normalized ratio). If you are not taking blood thinning medicines, such as warfarin, the normal range for your PT results is: 11 to 13.5 seconds. INR of 0.8 to 1.1.
