For patients who are taking blood-thinning drugs, such as warfarin, the normal level of PT/INR or prothrombin time expressed in international normalized ratio ranges from 2.0 to 3.0, states Mayo Clinic. This value is indicative of how fast or slow a patient's blood clots.
If a patient has a PT/INR value that is lower than normal, it means that his blood is clotting faster than desired, mentions Mayo Clinic. Conversely, a higher PT/INR value means that the patient's blood is clotting slower than desired. If a patient is not taking any blood-thinning medication, the PT value is generally measured in seconds, which has a normal range of 10 to 14 seconds.