International Normalized Ratio (INR) Targets: Venous Thromboembolism

Updated: Aug 05, 2021
Author: Joshua J Solano, MD, FAAEM, FACEP;

INR Targets in Venous Thromboembolism

International Normalized Ratio (INR) targets should only be used for the monitoring of warfarin. Warfarin is less commonly used for venous thromboembolism due to the advent of direct-acting oral anticoagulants (DOACs), which typically require no monitoring. Warfarin also requires bridging with low molecular weight heparin (LMWH) due to the delayed effects of getting to a therapeutic INR within the first few days of initiation.[1]  In cases where cost is a significant factor or DOACs are unavailable, the use of warfarin may be preferred. 

The guidelines below are based on the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines for Antithrombotic Therapy and Prevention of Thrombosis (ninth edition, 2012).[2]

Acute pulmonary embolism (PE)[3, 4]

International normalized ratio (INR) target (range)

  • Standard: 2.5 (2.0-3.0)

  • Unprovoked, infrequent INR checks: 1.5-1.9 after 3 months of standard therapy

Duration of therapy

  • Transient, reversible risk factor: 3 months

  • First episode, unprovoked

    • Low/moderate bleeding risk: Extended therapy

    • High bleeding risk: 3 months

  • Recurrent, unprovoked

    • Low/moderate bleeding risk: extended therapy

    • High bleeding risk: 3 months

  • Cancer: Extended therapy,  if recurrent venous thromboembolism (VTE) consider switching to LMWH[5]

Acute deep venous thrombosis (DVT) of the lower extremity

INR target (range)

  • Standard: 2.5 (2.0-3.0)

Duration of therapy

  • Transient, reversible risk factor: 3 months

  • First episode, unprovoked, proximal

    • Low/moderate bleeding risk: Extended therapy

    • High bleeding risk: 3 months

  • First episode, unprovoked, distal: 3 months (guidelines suggest serial imaging for 2 weeks rather than early anticoagulation for patients with isolated distal lower-extremity DVT who do not have severe symptoms or risk factors for extension)

  • Recurrent, unprovoked

    • Low/moderate bleeding risk: Extended therapy

    • High bleeding risk: 3 months

  • Cancer: Extended therapy if recurrent VTE consider LMWH[5]

Acute DVT of the upper extremity

INR target (range): 2.5 (2.0-3.0)[6]

Duration of therapy

  • Axillary or more proximal: 3 months or more

  • Distal: 3 months

  • Central venous catheter (CVC) related: Until catheter is removed, or a minimum of 3 months

Acute DVT in children

INR target (range)[7]

  • Standard: 2.5 (2.0-3.0)

  • CVC related: 1.5-1.9 after 3 months of standard therapy

Duration of therapy

  • Idiopathic, first episode: 6-12 months

  • Idiopathic, recurrent: Lifelong therapy

  • Reversible risk factor: Until risk factor has resolved, or a minimum of 3 months

  • Cancer, thrombophilia: Until risk factor has resolved, or a minimum of 3 months

  • CVC related: Until CVC is removed, or a minimum of 3 months