Prothrombin time (PT) measures how many seconds it takes your blood to clot.
- Normal range (adults)
- 11–13.5 seconds
- Sample
- Blood
- Fasting
- Not usually needed
- Also called
- Prothrombin Time, Protime, PT Seconds, Prothrombin Time PT
Prothrombin Time normal range
| Group | secondsSame unit in all countries |
|---|---|
| Adults | 11–13.5 |
Ranges vary slightly between laboratories. The range printed on your own report is the one to go by.
Why is the Prothrombin Time test done?
It is checked before surgery, in liver disease, and to monitor warfarin (usually reported as INR).
What does a high Prothrombin Time level mean?
A prolonged PT means blood takes longer to clot, increasing bleeding risk.
Common causes
- Warfarin
- Liver disease
- Vitamin K deficiency
- Some antibiotics
Diet and lifestyle tips
- If you take warfarin, keep vitamin K intake steady (leafy greens) rather than avoiding it
- Avoid alcohol
- Check with your doctor before starting supplements or herbal remedies
When should you see a doctor?
Seek care for unusual bleeding, black stools or blood in urine.
Last updated
This page is for general education and is not a diagnosis. Normal ranges differ between laboratories, so always compare your result with the reference range printed on your own report, and discuss abnormal results with your doctor.