PT INR Calculator

Calculate International Normalized Ratio (INR) values quickly and accurately for anticoagulation therapy monitoring

PT INR Calculator

INR Result

2.5
Within Therapeutic Range

About PT INR

The International Normalized Ratio (INR) is a standardized number that's calculated in the laboratory to monitor patients on anticoagulant therapy.

  • Normal Range: 0.8 - 1.2
  • Therapeutic Range: 2.0 - 3.0 (for most conditions)
  • High INR: Increased risk of bleeding
  • Low INR: Risk of clotting

Formula: INR = (Patient PT / Control PT)ISI

INR Interpretation Guide

Normal Range

0.8 - 1.2

Indicates normal blood clotting function. No anticoagulant effect present.

Therapeutic Range

2.0 - 3.0 (most cases)

Target range for patients on warfarin therapy. Provides balance between clotting prevention and bleeding risk.

High INR

Above 3.5

Increased risk of bleeding. May require dose adjustment or vitamin K administration.

Critical High

Above 5.0

Significant bleeding risk. Requires immediate medical attention and intervention.