What is the normal international normalized ratio (INR) range for a patient not on anticoagulation?

What is the normal international normalized ratio (INR) range for a patient not on anticoagulation?

• A. 0.9–1.3
• B. 0.7–1.0
• C. 0.85–1.15
• D. 0.8–1.1

Answer: (D)

INR is a standardized measure of how long blood takes to clot, and in someone not taking anticoagulants, the result should hover around 1.0. The reference interval commonly used for a healthy person is about 0.8 to 1.1, which centers near 1.0 and accommodates normal biological and lab variation. This is why the 0.8–1.1 range is the best choice—it reflects normal coagulation without anticoagulants. Other ranges either extend too far below or above the typical normal window or don’t center as close to 1.0, which is why they’re less appropriate as the normal reference for someone not on anticoagulation.

INR is a standardized measure of how long blood takes to clot, and in someone not taking anticoagulants, the result should hover around 1.0. The reference interval commonly used for a healthy person is about 0.8 to 1.1, which centers near 1.0 and accommodates normal biological and lab variation. This is why the 0.8–1.1 range is the best choice—it reflects normal coagulation without anticoagulants.

Other ranges either extend too far below or above the typical normal window or don’t center as close to 1.0, which is why they’re less appropriate as the normal reference for someone not on anticoagulation.