Prothrombin Test (PT), also known as Pro Time Test, is a blood test that measures how long it takes for blood to clot. Often used for identifying bleeding problems, it is also used to check if medicines (mostly Warfarin) that prevent blood clots are effectively working. A PT test is referred to as an INR Test, where INR stands for International Normalised Ratio and is a method of standardizing the results of the Prothrombin Test, irrespective of the testing method. This can be done using the INR System and enables the doctor to analyse reports from different labs. Prothrombin Test is important as it checks for the presence of five different blood clotting factors (factors I, II, V, VII, and X). Prothrombin or Factor II is made by the liver aided by a sufficient amount of Vitamin K. A doctor suggests a PT Test for symptoms such as excessive bleeding, bleeding gums, blood in urine or stool, heavy periods for women, bone marrow and liver problems, Vitamin K deficiency and leukemia.