Target INR Range for Warfarin Therapy

For most patients on warfarin, the target INR should be 2.5 with a therapeutic range of 2.0-3.0. 1, 2

Standard INR Targets by Clinical Indication

Atrial fibrillation with stroke risk factors requires an INR range of 2.0-3.0, as recommended by the American College of Cardiology and supported by FDA labeling 3, 2
Venous thromboembolism (deep vein thrombosis and pulmonary embolism) requires an INR range of 2.0-3.0 for all treatment durations 3, 2
Bioprosthetic heart valves require an INR of 2.0-3.0 for the first 3 months after valve insertion in both mitral and aortic positions 3, 2
Rheumatic mitral valve disease with history of systemic embolism or atrial fibrillation requires an INR of 2.0-3.0 3, 4

Mechanical heart valves with tilting disk or bileaflet valves in the mitral position require an INR target of 3.0 (range 2.5-3.5) 3, 2
Caged ball or caged disk mechanical valves require an INR of 2.5-3.5 in combination with aspirin 75-100 mg daily 3, 2
Patients at extremely high risk of stroke (valvular disease or prior stroke) may require an INR range of 2.5-3.5, though evidence does not show improved efficacy above 2.5 in atrial fibrillation 3

St. Jude Medical bileaflet valve in the aortic position requires only an INR of 2.0-3.0 in patients with normal sinus rhythm and normal left atrial size 3, 2

Patients 75 years and older may be managed with a lower target INR of 2.0 (range 1.6-2.5) for atrial fibrillation, as they face increased bleeding risk while maintaining approximately 80% of the thromboembolic protection 3
Elderly patients require approximately 1 mg/day less warfarin than younger individuals to maintain comparable INR prolongation 3

For mechanical prosthetic heart valves with persistent bleeding risk, a target INR of 2.0-2.5 is reasonable 3
For atrial fibrillation patients with prior bleeding, reducing the INR to 1.5-2.0 provides diminished but not abolished efficacy 3

INR values below 2.0 significantly increase the risk of thromboembolism and should prompt dose adjustment 1, 4
Low-intensity warfarin (INR ≤1.6) results in twice the risk of thrombotic events compared to adjusted-dose therapy (INR 2.0-3.0) 5

The risk of bleeding increases exponentially when INR exceeds 4.0 and becomes clinically unacceptable above 5.0 3, 1, 6
An INR greater than 4.0 provides no additional therapeutic benefit in most patients 2

Never target an INR below 2.0 for standard indications, as this lacks objective validation and provides inadequate protection against thromboembolism 1
Avoid high-intensity anticoagulation (INR 3.0-4.5) for non-cardioembolic stroke, as this was associated with 27 intracranial bleeds (17 fatal) versus 6 on aspirin in one major trial 3
Do not use loading doses when initiating warfarin, as this increases hemorrhagic complications without providing more rapid protection; start with 2-5 mg daily instead 2, 7
Recognize that bleeding at an INR of 3.0 is frequently associated with underlying lesions in the gastrointestinal or urinary tract, not just anticoagulation intensity 3