Prothrombin Time (PT) and International Normalized Ratio (INR)

Test Overview The PT test measures the exact time (in seconds) it takes for your blood plasma to form a clot via the extrinsic and common pathways of the coagulation cascade. Because testing materials vary across labs, the INR is a standardized calculation used worldwide to ensure your results are uniform and comparable, regardless of where your blood is tested. Why It Is Done (Clinical Purpose) Monitoring Warfarin/Coumadin Therapy: It ensures your dosage of oral blood-thinning medication is in the safe therapeutic range. Evaluating Liver Function: The liver synthesizes prothrombin and other crucial clotting factors; an abnormal PT can signal underlying liver disease. Diagnosing Bleeding Disorders: Investigates frequent nosebleeds, easy bruising, or heavy bleeding. Pre-Surgery Screening: Assesses bleeding risk before surgical procedures.