INR (International Normalized Ratio) is a standardised way of reporting prothrombin time so results are comparable worldwide.
- Normal range (adults)
- 0.8–1.2
- Sample
- Blood
- Fasting
- Not usually needed
- Also called
- International Normalized Ratio, INR Ratio, PT INR, Prothrombin INR
INR normal range
| Group | ValueSame unit in all countries |
|---|---|
| Adults | 0.8–1.2 |
Ranges vary slightly between laboratories. The range printed on your own report is the one to go by.
Why is the INR test done?
It is used to monitor warfarin, check liver function and assess bleeding risk before procedures.
What does a high INR level mean?
Above the normal range without warfarin suggests liver disease or vitamin K deficiency. On warfarin, most people aim for 2 to 3; above that raises bleeding risk.
Common causes
- Warfarin dose too high or interacting medicines
- Liver disease
- Vitamin K deficiency
Diet and lifestyle tips
- Keep vitamin K foods (spinach, broccoli, lettuce) steady from week to week
- Avoid alcohol binges
- Tell your doctor about any new medicine or supplement
What does a low INR level mean?
On warfarin, an INR below target means a higher clot risk.
Common causes
- Missed warfarin doses
- Sudden increase in vitamin K-rich foods
- Interacting medicines
Diet and lifestyle tips
- Take warfarin at the same time every day
- Keep greens steady rather than suddenly increasing them
When should you see a doctor?
On warfarin, follow your clinic's schedule. Seek urgent care for heavy bleeding.
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.