Prothrombin Time (PT)
CoagulationNormal range
11–12.5 seconds
SI: 11–12.5 s
Critical high: > 40 s (not on warfarin)
☎ When to call
Escalate via the INR and any bleeding signs — see INR card.
What you do
- For warfarin monitoring, use the INR — PT alone varies by lab
- Prolonged without warfarin? Look at the liver and nutrition
Causes of HIGH prothrombin time
Causes of LOW prothrombin time
Source: Pagana, Mosby's Manual of Diagnostic and Laboratory Tests, 7th ed.Reference only — verify against your facility's policy.
