The international normalized ratio or INR is a formula that doctors use to standardize the results of prothrombin time tests, helping them understand results from different testing methods or laboratories, explains WebMD. The prothrombin time test measures the time blood takes to clot and checks for bleeding problems.
Patients who regularly have their blood tested, such as those taking the anticoagulant warfarin, can travel and obtain comparable INR results regardless of where they are, notes MedicineNet. A measure between 2.0 and 3.0 is considered effective and indicates that the blood clots as desired, states Mayo Clinic. An INR below this range means that blood is clotting more quickly, and a result above this range means that blood clots at a slower rate than recommended.