Prothrombin time (PT)
Prothrombin time (PT) is a blood test that measures the time it takes for the liquid portion (plasma) of your blood to clot.
Most of the time, results are given as what is called INR (international normalized ratio). If you are not taking bloodthinning medicines, such as warfarin, the normal range for your PT results is: 11 to 13.5 seconds. INR of 0.8 to 1.1.