What is a normal INR target?

For most conditions (atrial fibrillation, DVT/PE, mechanical aortic valve): INR 2.0–3.0. For mechanical mitral valve or recurrent thromboembolism: INR 2.5–3.5. The target range depends on the indication for anticoagulation.

How do I adjust warfarin doses?

General principles: dose changes of 5–15% of the weekly dose are typical. Wait at least 3–5 days after a dose change before rechecking INR (warfarin has a long half-life). Keep a dosing diary and monitor for signs of bleeding or clotting.

Many factors affect INR: diet (vitamin K in green vegetables), other medications (antibiotics, NSAIDs, amiodarone), alcohol, liver disease, thyroid changes, illness, and genetic variations in CYP2C9 and VKORC1 enzymes.

What should I do for a high INR?

INR 4.5–5: hold 1–2 doses, reduce dose. INR 5–9: hold warfarin, consider vitamin K 1–2.5 mg orally. INR > 9: hold warfarin, give vitamin K, consider emergency department if any bleeding. Always check for signs of active bleeding.

Online Medical Tools — Warfarin Guidance

Printed on 2/13/2026

For informational purposes only. This is not medical advice.

Warfarin Guidance

Warfarin is a commonly used anticoagulant that requires careful dose titration based on the International Normalized Ratio (INR). This tool provides evidence-based dose adjustment guidance based on the patient's current INR relative to their target INR range. It covers scenarios from sub-therapeutic to dangerously elevated INR levels with specific action recommendations.

Compare with HAS-BLED Score

Formula: Evidence-based INR-guided dose adjustment recommendations

Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.