Warfarin INR Ranges
Standard Therapeutic Target
For most indications including atrial fibrillation, venous thromboembolism (DVT/PE), and rheumatic heart disease, target an INR of 2.0-3.0 (goal 2.5). 1, 2, 3
This represents the standard intensity anticoagulation that balances thrombotic protection against bleeding risk across the broadest range of clinical scenarios. 4, 1
INR Targets by Clinical Indication
Standard Intensity (INR 2.0-3.0)
- Atrial fibrillation with stroke risk factors 1, 2, 3
- Deep vein thrombosis and pulmonary embolism (first episode or recurrent) 1, 2, 3
- Valvular heart disease (rheumatic mitral valve, bioprosthetic valves for first 3 months) 1, 2, 3
- Dilated cardiomyopathy 2
- Antiphospholipid syndrome (both venous and arterial thrombosis) 5
- St. Jude Medical bileaflet valve in aortic position 3
Higher Intensity (INR 2.5-3.5)
- Mechanical heart valves (tilting disk or bileaflet in mitral position) 1, 2, 3
- Caged ball or caged disk valves (combined with aspirin 75-100 mg/day) 3
- Post-myocardial infarction high-risk patients (in select healthcare settings with meticulous INR monitoring) 3
Historical Higher Intensity (No Longer Recommended)
- The older target of INR 3.0-4.5 has been abandoned because lowering to INR 2.0-3.0 markedly reduces bleeding risk without compromising efficacy. 4
Critical Thresholds for Safety
Subtherapeutic Range
- INR <2.0 significantly increases thromboembolism risk and provides inadequate protection. 1, 2
- Targeting INR ranges below 2.0 (such as 1.5-2.0) lacks objective validation and should be avoided except in specific circumstances where bleeding risk is catastrophic. 1
Supratherapeutic Range
- INR >4.0: Bleeding risk increases exponentially. 1
- INR ≥5.0: Bleeding risk becomes clinically unacceptable and sharply elevated. 1, 6
- INR >9.0: Requires intervention with vitamin K even without active bleeding. 1
Monitoring Strategy
Initial Phase
- Check INR daily until therapeutic range is reached and sustained for 2 consecutive days. 1, 2
- Then monitor 2-3 times weekly for 1-2 weeks. 1, 2
- Then weekly for 1 month. 1, 2
Maintenance Phase
- Once stable, extend monitoring intervals up to every 4-12 weeks (maximum 4-6 weeks is most commonly recommended). 1, 2, 7
- Increase monitoring frequency during diet changes, medication changes, weight fluctuations, or intercurrent illness. 1, 2
Single Out-of-Range Value
- For INR ±0.5 from target without bleeding, continue current dose and retest within 1-2 weeks. 2
- Do not adjust dose for a single slightly out-of-range INR in stable patients. 7
Management of Elevated INR
INR 4.0-5.0 (No Bleeding)
INR 5.0-9.0 (No Bleeding)
- Omit 1-2 doses of warfarin. 1, 2
- Consider oral vitamin K 1-2.5 mg if patient has bleeding risk factors. 1
INR >9.0 (No Bleeding)
Life-Threatening Bleeding or Major Overdose
- Vitamin K 10 mg by slow IV infusion over 30 minutes. 4, 1
- Plus fresh frozen plasma or prothrombin complex concentrate depending on urgency. 4, 1
Special Populations and Pitfalls
Elderly Patients
- Patients ≥75 years require approximately 1 mg/day less than younger individuals to maintain comparable INR. 4
- Consider lower initial doses (2-4 mg) rather than standard 5 mg. 7
- Elderly patients have higher bleeding risk even at therapeutic INR levels. 4
Antiphospholipid Syndrome
- Do NOT use rivaroxaban or other DOACs in triple-positive antiphospholipid syndrome—this carries excess thrombotic risk compared to warfarin (Class 3 Harm recommendation). 5
- Maintain standard INR 2.0-3.0 even for high-risk patients with lupus anticoagulant and multiple antibodies. 5
Perioperative Management
- Stop warfarin 5 days before surgery to allow INR to decrease to ≤1.5. 4
- Check INR the day before surgery; if ≥1.8, give oral vitamin K 1-2.5 mg. 4
- Avoid high-dose vitamin K (>5 mg) as it may cause warfarin resistance lasting up to one week. 1
Common Dosing Errors to Avoid
- Avoid loading doses—they increase hemorrhagic complications without providing faster protection. 3, 7
- Start with 2-5 mg daily (lower end for elderly/debilitated patients). 3, 7
- Most dose adjustments should alter the total weekly dose by 5-20%, not make dramatic daily changes. 7
Evidence Quality Note
The INR 2.0-3.0 target is supported by multiple randomized trials demonstrating that this range provides optimal efficacy while the older higher-intensity ranges (3.0-4.5) significantly increased bleeding without additional thrombotic protection. 4 This recommendation is consistent across the American College of Cardiology, American Heart Association, American Geriatrics Society, and FDA labeling. 4, 1, 2, 3