The nurse is caring for an older adult patient with a decrease in kidney function. Which of the following laboratory values should the nurse monitor?

A. Complete Blood Count: A CBC evaluates red and white blood cells and platelets, which are not direct indicators of kidney function. While anemia can develop in chronic kidney disease, CBC changes are secondary and do not provide immediate information about renal clearance. B. Creatinine: Serum creatinine is a primary marker of kidney function because it reflects the kidneys’ ability to filter waste products. Elevated levels indicate impaired glomerular filtration rate (GFR) and help guide medication dosing and fluid management in older adults. C. Serum Sodium and Potassium: Electrolytes can be affected by kidney impairment, but changes often occur after kidney function declines significantly. While important to monitor for complications such as hyperkalemia or hyponatremia, these values are not as sensitive as creatinine for detecting early decreases in renal function. D. Serum Albumin: Albumin measures protein status and nutritional health rather than kidney filtration ability. Low levels may be seen in nephrotic syndrome but are not a reliable indicator of general kidney function.