A blood urea nitrogen, or BUN, test is a blood test that determines the blood nitrogen level, according to WebMD. Typically, a doctor performs a BUN test to determine the efficiency of the kidneys, check the progress of kidney disease, and check the effectiveness of a kidney disease treatment.
Before the BUN test, the doctor advises the patient to avoid eating excess proteins, including meat, at least one day prior to the test as proteins may affect the accuracy of the test results, explains WebMD. To perform the test, a technician first stops the blood flow by wrapping the upper arm with an elastic band. He sterilizes the injection site with alcohol, inserts a needle into a vein in the arm, and draws the blood into a syringe. Once the technician draws enough blood, he undoes the band and withdraws the needle while pressing a cotton ball against the injection site. He then puts a bandage over the site and sends the blood to a lab for analysis.
Although the BUN test is often a safe procedure, it may result in phlebitis, which is the inflammation of the vein following a blood sample draw, warns WebMD. Drawing a blood sample from people with clotting disorders may also be problematic as it may result in prolonged bleeding. The needle can also cause bruises during the injection.