What is the normal range for PTT without anticoagulation?

What is the normal range for PTT without anticoagulation?

• A. 40-60 seconds
• B. 10-20 seconds
• C. 20-40 seconds
• D. 60-80 seconds

Answer: (C)

PTT measures how long plasma takes to clot via the intrinsic and common pathways. In someone not on anticoagulants, the normal range is roughly 20 to 40 seconds (with many labs around 25–35 seconds, but values can vary by reagents). This broad range accounts for lab-to-lab differences while reflecting typical physiology. Values longer than this, such as 60–80 seconds, suggest an abnormality or anticoagulation; values shorter than about 20 seconds are not considered normal. Therefore, 20–40 seconds is the best representation of the normal range without anticoagulation.