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 ...

When you get a cut, your body jumps into action to keep things from getting out of hand. Cells called platelets get there first to slow the bleeding. Then, a bunch of proteins, called clotting factors ...