Before administering warfarin 5 mg to a client, which laboratory values should the nurse check?

When administering warfarin, it is crucial to monitor the prothrombin time (PT) and the international normalized ratio (INR) because warfarin is an anticoagulant that requires careful management of blood coagulation levels. PT is a laboratory test that measures the time it takes for blood to clot, while the INR is a standardized measure that compares the patient's PT to a normal range. These values are vital in determining whether the dosage of warfarin is appropriate for the patient, helping to minimize the risk of both clotting and bleeding complications.

Before administering warfarin, the nurse must ensure that the INR is within the therapeutic range, which typically falls between 2.0 and 3.0 for most conditions requiring anticoagulation, although this may vary based on specific clinical scenarios. If the INR is too low, the patient is at risk for thrombosis; if it is too high, there is an increased risk of bleeding. Checking PT and INR allows the nurse to evaluate the effectiveness of the warfarin therapy and guide any necessary dosage adjustments.