Which test is used to evaluate kidney function by measuring urea nitrogen in the blood?

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

Answer: (A)

Measuring urea nitrogen in the blood gauges how well the kidneys are clearing waste from the body. Urea, produced in the liver from protein breakdown, travels in the blood and is normally filtered out by the kidneys into urine. If kidney function is impaired, urea isn’t cleared efficiently, so the blood urea nitrogen level rises. Because BUN is influenced by factors like hydration and protein intake, clinicians often interpret it alongside creatinine and consider the BUN/creatinine ratio for a clearer picture of kidney function. The other tests listed assess different body systems: a complete blood count looks at blood cells, a calcium test checks calcium levels, and a bone scan visualizes bone structure. The test that evaluates kidney function by measuring urea nitrogen in the blood is the blood urea nitrogen test.