A nurse is preparing to administer a daily dose of warfarin to a client. Which of the following laboratory values should the nurse check prior to administration?

A. WBC: White blood cell count is unrelated to warfarin therapy. B. INR: Warfarin’s anticoagulant effect is monitored using the International Normalized Ratio (INR). A therapeutic INR range is typically 2–3 for most indications. C. Platelets: While platelets are important for overall clotting, INR is the specific measure for warfarin. D. APTT: Activated partial thromboplastin time (APTT) is used to monitor heparin, not warfarin.