Recommended INR Range for Atrial Fibrillation

For patients with atrial fibrillation on warfarin, the recommended INR target range is 2.0 to 3.0, with an optimal target of 2.5. 1, 2, 3

Standard INR Target

The INR range of 2.0 to 3.0 is universally recommended across all major guidelines including the American College of Cardiology, American Heart Association, and American College of Chest Physicians for patients with nonvalvular atrial fibrillation 4, 1, 2, 3
This target applies regardless of whether the atrial fibrillation pattern is paroxysmal, persistent, or permanent 4, 2
The same INR target of 2.0 to 3.0 applies to atrial flutter as well 4, 2
An optimal target INR of 2.5 maximizes time spent in the therapeutic range and provides the best balance between stroke prevention and bleeding risk 1, 5

Multiple randomized controlled trials demonstrate that INR 2.0 to 3.0 provides maximum protection against ischemic stroke while minimizing bleeding complications 1, 2, 6
Lower INR targets (1.6 to 2.5 or 1.5 to 2.0) provide only approximately 80% of the stroke protection achieved with standard-intensity anticoagulation 1, 2
Meta-analysis shows that adjusted-dose warfarin (INR 2.0-3.0) compared with lower dose warfarin (INR ≤1.6) significantly reduces thrombotic events (RR 0.50,95% CI 0.25-0.97) without increasing major bleeding 7
Recent pooled data from modern trials (RELY, ARISTOTLE, ENGAGE AF-TIMI 48) confirms that INR between 2.0 and 2.5 provides the lowest combined risk of ischemic stroke and intracranial hemorrhage 5
A 2020 meta-analysis of 79 RCTs (n=12,928) demonstrated that lower INR targets increase thromboembolism by 50% (RR 1.50,95% CI 1.29-1.74) compared to standard targets 8

While some older guidelines suggested a lower target INR of 2.0 (range 1.6-2.5) for elderly patients, more recent and robust guidelines maintain the standard 2.0-3.0 range for all age groups 4, 1, 2
Age alone is not a contraindication to standard-intensity anticoagulation, though bleeding risk should be carefully assessed 4

Patients with mechanical heart valves require warfarin (not DOACs) with target INR of at least 2.5 4, 2
For St. Jude Medical bileaflet valves in the aortic position: target INR 2.5 (range 2.0-3.0) 3
For tilting disk or bileaflet valves in the mitral position: target INR 3.0 (range 2.5-3.5) 4, 3
For caged ball or caged disk valves: target INR 3.0 (range 2.5-3.5) 4, 3

INR should be checked at least weekly during warfarin initiation until stable therapeutic levels are achieved 4, 2
Once stable in therapeutic range, INR monitoring should occur at least monthly 4, 2
Time in therapeutic range (TTR) should be ≥65-70% to maximize efficacy and safety 1, 2
Patients with TTR <65% have significantly higher risk of stroke/systemic embolism (HR 2.55), mortality (HR 2.39), and major bleeding (HR 1.54) 1

Some Asian countries have proposed lower target INR ranges (1.6-2.6), especially in elderly patients 1
Current guidelines explicitly state there is no robust evidence for implementing lower INR targets of 1.6 to 2.6, and the conventional evidence-based target of 2.0 to 3.0 should be employed globally 1, 2
The 2020 meta-analysis concluded that until higher quality data demonstrate otherwise, an INR range of 2.0 to 3.0 should remain standard for thromboembolic prophylaxis in AF 8

Do not use lower INR targets (1.5-2.0) thinking they are safer – they significantly increase stroke risk without proportionally reducing bleeding 1, 7, 8
Random "one-off" INR values provide little insight into anticoagulation quality; focus on average TTR over time 1
Many adverse outcomes (including bleeding) can occur even within the therapeutic INR range of 2.0-3.0, highlighting the importance of consistent monitoring 1
If TTR remains <65% despite optimization efforts, consider switching to a DOAC rather than accepting subtherapeutic anticoagulation 1, 2