A nurse is reviewing the laboratory data of a client who has chronic renal failure and is to receive epoetin alfa subcutaneously. Which of the following values should the nurse monitor to evaluate the effectiveness of the medication?

A. Sodium is not directly related to the effectiveness of epoetin alfa, which stimulates red blood cell production. B. WBC count is not the primary marker for evaluating epoetin alfa therapy. C. Glucose is not a key indicator of epoetin alfa effectiveness. D. Hemoglobin is the key indicator because epoetin alfa is used to stimulate red blood cell production in clients with anemia due to chronic renal failure. The goal is to increase hemoglobin levels.