What is the therapeutic INR for warfarin for most patients?

• A. 1-2
• B. 2-3
• C. 3-4
• D. 0.5-1.5

Answer: (B)

Warfarin is aimed at tipping the balance between preventing clots and avoiding excess bleeding, and for most patients the target is an INR of about 2.0 to 3.0. This range provides effective protection against thromboembolism in common indications (like nonvalvular atrial fibrillation or venous thromboembolism treatment) while keeping bleeding risk at a manageable level. If the INR is too low, anticoagulation isn’t enough and clots can still form; if it’s too high, the risk of serious bleeding rises. The ranges outside 2.0–3.0 are either subtherapeutic or overly anticoagulated for the majority of patients. There are exceptions, such as certain mechanical heart valve situations, where a higher target range may be used, but for most people the standard goal is 2.0–3.0.