Explain the Blood Urea Nitrogen (BUN)

It is a test that measures the amount of urea nitrogen in the blood. Urea is formed in the liver as an end product of protein metabolism and is carried to the kidneys for excretion. During digestion, protein is broken down to amino acids. Amino acids contain nitrogen, which is removed as ammonium ion), while the rest of the molecule is used to produce energy or other substances needed by the cell. The ammonia combines with other small molecules to produce urea.

The urea makes its way into the blood and is ultimately eliminated in the urine by the kidneys. Nearly all kidney diseases cause an inadequate excretion of urea, elevating BUN levels in the blood. Other causes of high BUN levels include dehydration, gastrointestinal bleeding, steroid treatment and use of many other drugs compete with urea for elimination by the kidneys. The normal values for the test are: 7 to 20 mg/dl and the abnormal results indicate many diseases.