What laboratory test is often ordered to assess kidney function?

Blood urea nitrogen (BUN) is a laboratory test specifically used to assess kidney function. It measures the amount of urea nitrogen in the blood, which is a waste product formed in the liver after the body breaks down protein. Under normal circumstances, the kidneys filter out urea and excrete it in urine. When kidney function is impaired, the levels of urea in the blood can increase, making BUN a crucial marker for evaluating renal health.

In contrast, a complete blood count provides information on various blood components, such as red and white blood cells and platelets, but does not directly assess kidney function. A lipid profile measures the levels of different types of fats in the blood, including cholesterol, which is important for cardiovascular health but not related to kidney performance. Thyroid function tests evaluate how well the thyroid gland is working and are not indicative of kidney health. Therefore, the significance of blood urea nitrogen in evaluating kidney function makes it the appropriate choice among the options presented.