Elevated levels of which lab value indicate reduced kidney function?

• A. Calcium test
• B. Cholesterol test
• C. Blood urea nitrogen (BUN)
• D. Complete blood count

Answer: (C)

Elevated levels of blood urea nitrogen (BUN) reflect reduced kidney function because urea is a waste product from protein breakdown that is normally filtered out by the kidneys. When filtration declines, urea accumulates in the blood, raising the BUN value. BUN interpretation should consider hydration and protein intake, and is typically assessed alongside creatinine and the BUN/creatinine ratio. The other tests measure calcium, cholesterol, or blood cell components, which are not direct indicators of how well the kidneys are filtering.