PT/INR is a blood test that basically tests how quickly your blood clots. PT and INR are actually two different readings that a physician or pharmacist uses to determine the degree to which your blood is being anticoagulated. PT stands for Prothrombin Time and literally measures the number of seconds it takes your blood to clot. INR stands for International Normalized Ratio and is a Ratio of the patient’s PT in seconds over a standard PT in seconds and multiplied by an ISI (International Sensitivity Index) of 1.0.
The INR is most commonly used to adjust ones Coumadin or warfarin dosage in order to keep a patient within their deemed safe therapeutic range. Most patients have an INR range prescribed of 2.0 – 3.0 but some patients with mechanical heart valves may have an INR range of 2.5 – 3.5 or a bit higher.
If ones INR is below the the safe therapeutic range you may be at a higher risk of having a blood clot form and if your INR is above the safe therapeutic range you may be at a higher risk of serious internal bleeding.