The nurse observes that a client is experiencing melena. Which serum laboratory test should the nurse monitor in response to this finding?

Rationale: A. Glucose: Monitoring glucose levels is important for clients with diabetes or metabolic concerns, but it does not provide direct information about blood loss. Melena indicates gastrointestinal bleeding, and glucose measurements would not help evaluate the severity of this blood loss. B. White blood cell count (WBC): A WBC count can detect infection or inflammation but is not the primary concern in a client with melena. Since melena suggests gastrointestinal bleeding, monitoring for anemia or hypovolemia is far more critical than assessing for infection at this point. C. Blood urea nitrogen (BUN): BUN levels may rise with upper gastrointestinal bleeding due to the digestion of blood proteins. However, while helpful in some cases, BUN is less directly reflective of the immediate clinical impact of blood loss compared to hematocrit, which assesses the blood’s oxygen-carrying capacity. D. Hematocrit: Hematocrit measures the proportion of red blood cells in the blood and is a critical indicator of anemia and blood loss severity. In clients with melena, monitoring hematocrit helps evaluate the extent of bleeding and the need for interventions like fluid replacement or transfusion.