The prothrombin time test, or international normalized ratio test, is administered in a medical lab facility to help a doctor determine if a patient has issues with blood clotting. The normal range for blood clotting is 11 to 13 seconds, as referenced by WebMD. A phlebotomist or nurse will take a vial of blood and add specially formulated chemicals to the sample and then time how long it takes until the plasma clots.Continue Reading
The prothrombin time test is used for patients who take blood-thinning medications to ensure that the blood still clots normally. Doctors can use the results of this test to change the dosage of blood-thinning medications or prescribe a different medication for patients with blood clotting problems.
This test is also used to diagnose blood-clotting disorders, check for liver problems, check for a lack of vitamin K or certain blood-clotting factors, according to MedlinePlus. The test is simple, and the greatest risk for those with a clotting disorder is having trouble getting the bleeding to stop after the blood is drawn.
Labs will vary in the ranges used to determine if the prothrombin time test is normal, so it is always best to let a doctor read the results and recommend treatment.Learn more about Standardized Tests