What is the ideal INR range for patients on anticoagulation therapy (e.g., for atrial fibrillation or mechanical heart valves)?

Correct answer: D. 2.0–3.0 (therapeutic range for most conditions)

• A. INR 1.0–1.5 is subtherapeutic — the patient is not adequately anticoagulated and at increased clotting risk.
• B. INR 3.5–4.0 is supratherapeutic and indicates increased bleeding risk.
• C. INR of 1.0 is the normal (non-anticoagulated) baseline.
• D. Correct. The therapeutic INR range for most anticoagulation indications (atrial fibrillation, venous thromboembolism, most mechanical valves) is 2.0–3.0. Higher ranges (2.5–3.5) may be used for mechanical mitral valves. For dental extractions, current guidelines support proceeding when INR is ≤3.5 without stopping warfarin.