– PT: Prothrombin Time – Time needed for blood to coagulate/clot ; provides a benchmark for efficacy of warfarin therapy (Coumadin). Not used as much as INR is used to measure warfarin effectiveness. 🩸Expected Range: Not on warfarin therapy: 10-14 seconds On warfarin therapy: 1.5-2x the original value – INR: International Normalized Ratio – A number derived FROM the PT (this is SO important to know!) ; provides benchmark for efficacy of warfarin therapy (Coumadin) ⭐INR is more widely used for t

INR (International Normalized Ratio) and PT (Prothrombin Time) are closely related, but they differ in how they’re used and standardized: 1. Prothrombin Time (PT): PT measures the time (in seconds) it takes for blood to clot. Usually 11-13.5 sec. It’s specifically testing the extrinsic pathway of the coagulation system, which involves certain clotting factors (e.g., Factors I, II, V, VII, and X). PT results can vary between labs due to differences in testing methods and reagents. So… 2. Internat