The nurse is caring for a client who is taking diclofenac for rheumatoid arthritis. During a clinic visit, the client appears pale and reports increasing fatigue. Which of the client's serum laboratory values is most important for the nurse to review?

A. Sodium: Monitoring sodium is important in many conditions, but diclofenac, a nonsteroidal anti-inflammatory drug (NSAID), is more commonly associated with gastrointestinal bleeding rather than causing significant electrolyte imbalances like hyponatremia. Sodium levels are not the primary concern in this scenario. B. Glucose: Blood glucose monitoring is critical for clients with diabetes or corticosteroid use, but diclofenac is not known to directly impact glucose metabolism. Reviewing glucose levels would not immediately address the symptoms of pallor and fatigue. C. Total protein: Total protein levels reflect nutritional and liver status but are not the best marker for acute blood loss or anemia. Changes in total protein would not directly explain symptoms like pallor and fatigue related to NSAID complications. D. Hemoglobin: Diclofenac can cause gastrointestinal irritation and occult bleeding, leading to anemia. Pallor and fatigue are classic symptoms of low hemoglobin levels, making it the most important laboratory value to review to evaluate for possible GI bleeding and anemia.