Prothrombin time (PT).

A prothrombin time (PT) test measures the amount of time it takes for your blood plasma to clot. Prothrombin, also known as factor II, is just one of many plasma proteins involved in the clotting process.

If your doctor suspects you have a bleeding disorder, they may order a PT test to help them make a diagnosis. Even if you have no symptoms of a bleeding disorder, your doctor may order a PT test to make sure your blood is clotting normally before you undergo major surgery.

If you’re taking the blood-thinning medication warfarin, your doctor will order regular PT tests to ensure you’re not taking too much medication. Taking too much warfarin can cause excessive bleeding.

Liver disease or vitamin K deficiency can cause a bleeding disorder.