The normal range for pro-time, also known as prothrombin time, is 11 to 13 seconds, according to WebMD. The value is determined in a laboratory by taking a blood sample and measuring the time necessary for a blood clot to form.Continue Reading
Prothrombin is a protein found in the blood which aids in the formation of clots, as described by Mayo Clinic. A prothrombin test is ordered to screen for liver problems and bleeding disorders, as well as to determine if blood-thinning medications, such as warfarin, are within a therapeutic range. Surgeons also order a prothrombin time test in preparation for surgery to ensure that there are no undetected bleeding disorders that could cause complications.
Laboratories use different chemicals and methods to measure prothrombin time, which results in variable reference ranges, as reported by WebMD. To provide a more standardized measurement of clotting time which is comparable from lab to lab, prothrombin time is also reported as a ratio known as the international normalized ratio, or INR. In the absence of blood-thinning medication, the normal INR range is 0.8 to 1.1. If anti-coagulation is medically indicated, an INR range of 2.0 to 3.0 is generally considered effective, according to Mayo Clinic.Learn more about Medical Ranges & Levels