Which laboratory test is used to evaluate kidney function?

The Blood Urea Nitrogen (BUN) test is specifically designed to assess kidney function. It measures the level of urea nitrogen in the blood, which is a waste product formed from the breakdown of proteins. Under normal circumstances, kidneys filter urea from the blood and excrete it in urine. A high level of BUN can indicate impaired kidney function, as the kidneys may not be filtering effectively, leading to the accumulation of waste products in the bloodstream.

Other tests mentioned serve different purposes: the Complete Blood Count (CBC) is used to evaluate overall health and detect a variety of disorders, such as infection and anemia, but does not provide direct insight into kidney function. The blood glucose test measures blood sugar levels and is primarily used to diagnose and manage diabetes. Urinalysis evaluates various aspects of urine, such as its composition and specific gravity, and can give indirect indications of kidney function, but does not serve as a direct measurement like BUN does. Therefore, BUN is a critical and direct marker for assessing the filtering capacity of the kidneys.