BUN

The blood urea nitrogen (BUN) test is a measure of the amount of nitrogen in the blood that comes from urea. Urea is a substance secreted by the liver, and removed from the blood by the kidneys. Methodology The test as originally carried out was by flame photometry; now chemical colorimetric tests are more widely used. Physiology The liver produces urea in the urea cycle as a waste product of the digestion of protein. Normal human adult blood should contain between 7 and 25 mg of urea ...