INR for a patient not on warfarin is typically below which value?

INR for a patient not on warfarin is typically below which value?

• A. 0.5-1.0 second
• B. <1 second
• C. 1-2 seconds
• D. 2-3 seconds

Answer: (B)

INR measures how long the blood takes to clot, and in someone not taking warfarin the baseline INR is about 1.0, meaning normal clotting tendency. Warfarin therapy raises INR into a therapeutic range (often around 2–3, depending on the indication). The values shown are in seconds, which actually reflect prothrombin time (PT) rather than INR, so the format doesn’t fit INR precisely. The key idea is that not on warfarin, the clotting time should be normal (INR ~1.0). Among the given options, the value representing no prolonged clotting tendency—the smallest value on that scale—best aligns with a non-anticoagulated state, which is why this option is chosen.

INR measures how long the blood takes to clot, and in someone not taking warfarin the baseline INR is about 1.0, meaning normal clotting tendency. Warfarin therapy raises INR into a therapeutic range (often around 2–3, depending on the indication). The values shown are in seconds, which actually reflect prothrombin time (PT) rather than INR, so the format doesn’t fit INR precisely. The key idea is that not on warfarin, the clotting time should be normal (INR ~1.0). Among the given options, the value representing no prolonged clotting tendency—the smallest value on that scale—best aligns with a non-anticoagulated state, which is why this option is chosen.