Malnutrition is most commonly indicated by which laboratory changes?

• A. Decreased prealbumin and BUN
• B. Increased prealbumin and BUN
• C. Decreased albumin only
• D. Elevated creatinine

Answer: (A)

Understanding how nutrition affects lab values helps explain why this pattern fits malnutrition. Prealbumin responds quickly to changes in protein intake because it has a short half-life, so it decreases when nutritional status worsens. BUN reflects the amount of protein being metabolized; with inadequate protein intake, less urea is produced, so BUN falls. Albumin changes more slowly and can be influenced by inflammation, hydration, and liver function, making it less reliable for detecting recent malnutrition. Creatinine is tied more to kidney function and muscle mass than to nutritional status, so it’s not a direct marker of malnutrition. Therefore, the combination of decreased prealbumin and decreased BUN best indicates malnutrition.