What blood test to determine kidney function by measuring the level of nitrogenous waste in the blood?

The blood test used to determine kidney function by measuring the level of nitrogenous waste in the blood is called the Blood Urea Nitrogen (BUN) test. Elevated levels of BUN can indicate impaired kidney function, as the kidneys are responsible for filtering urea, a waste product formed from protein metabolism. This test is often used in conjunction with other tests, such as serum creatinine, to assess overall kidney health.