– 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