Prothrombin Time (PT / INR)

Prothrombin time measures how long blood takes to clot; INR expresses the same result on a standard scale shared by all labs.

People on warfarin test it regularly — the target is often between 2 and 3 depending on the condition. Doctors also order it before surgery and to follow liver function.

Preparation before the test

• Take your warfarin dose at the usual time and note when you took the last one.
• Tell the lab about the medicines you take.

This information is for awareness only and is not a substitute for medical advice — your treating doctor interprets the result for your case.