Prothrombin time (PT): MedlinePlus Medical Encyclopedia
Prothrombin time (PT) is a blood test that measures the time it takes for the liquid portion (plasma) of your blood to clot. It measures the function of a part of the clotting system. ... What Abnormal Results Mean. If you are not taking blood thinning medicines, such as warfarin, an INR result above 1.1 means your blood is clotting more slowly ...