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. 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).

Acute pulmonary embolism (PE)^�

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

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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

Acute DVT of the upper extremity

INR target (range): 2.5 (2.0-3.0)^�

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)^�

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

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