Which laboratory value is most commonly used as an indicator of kidney function and is typically elevated in renal failure?

• A. Blood Urea Nitrogen
• B. Creatinine
• C. Sodium
• D. Glucose

Answer: (B)

Creatinine is produced at a relatively constant rate by muscle and is cleared from the body almost entirely by the kidneys through glomerular filtration. Because of this direct relationship with filtration, the serum creatinine level closely reflects how well the kidneys are functioning. When kidney function declines, the glomerular filtration rate falls and creatinine accumulates, leading to an elevated blood creatinine level. This makes creatinine a reliable and commonly used indicator of kidney function and a standard marker for detecting renal failure.

Blood urea nitrogen can rise for reasons beyond kidney function, such as dehydration or high protein intake, so it’s less specific. Sodium and glucose levels aren’t direct measures of kidney filtering ability, so they don’t serve as the primary markers of renal function.