INR Calculator - International Normalized Ratio

Your details

The prothrombin time measured from your blood sample, in seconds. Reported on your lab result slip.
seconds
The mean normal prothrombin time for the local laboratory, usually 11-14 seconds. Found on your lab report or provided by the testing facility.
seconds
International Sensitivity Index - a calibration factor supplied by the reagent manufacturer. Values typically range from 0.9 to 1.7. A value of 1.0 means the reagent is perfectly calibrated to the WHO reference.
Choose the condition being monitored to see the relevant therapeutic target range alongside your INR.
INRElevated - may be subtherapeutic
1.5

International Normalized Ratio

PT ratio1.5
Target range low2
Target range high3
Therapeutic statusBelow target (2.0-3.0) - subtherapeutic
1.5 INR
Normal<1.1Subtherapeutic1.1-2Therapeutic2-3Borderline3-3.5Elevated3.5-5Critical5+

INR 1.50 - subtherapeutic

  • Your INR of 1.50 is below the therapeutic range (2.0-3.0) for Atrial fibrillation. Clot protection may be insufficient.
  • INR should always be interpreted alongside clinical symptoms and recent medication changes. Never adjust warfarin dose without guidance from your prescriber.

Next stepDiscuss dose adjustment or adherence with your anticoagulation team at your next scheduled check.

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