BUN stands for blood urea nitrogen. Urea nitrogen is what forms when protein breaks down.
A test can be done to measure the amount of urea nitrogen in the blood.
Alternative Names
Blood urea nitrogen
How the test is performed
A blood sample is needed. For information on how this is done, see: Venipuncture
How to prepare for the test
Many drugs affect BUN levels. Before having this test, make sure the health care provider knows which medications you are taking.
Drugs that can increase BUN measurements include:
Allopurinol
Aminoglycoside antibiotics
Amphotericin B
Aspirin (high doses)
Bacitracin
Carbamazepine
Cephalosporins
Chloral hydrate
Cisplatin
Colistin
Furosemide
Guanethidine
Indomethacin
Methicillin
Methotrexate
Methyldopa
Neomycin
Penicillamine
Polymyxin B
Probenecid
Propranolol
Rifampin
Spironolactone
Tetracyclines
Thiazide diuretics
Triamterene
Vancomycin
Drugs that can decrease BUN measurements include:
Chloramphenicol
Streptomycin
How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
The BUN test is often done to check kidney function.
Normal Values
The normal result is generally 6 - 20 mg/dL.
Note: Normal values may vary among different labs. Talk to your doctor about your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks are slight but may include:
Excessive bleeding
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Special considerations
For people with liver disease, the BUN level may be low even if the kidneys are normal.
References
Clarkson MR, Friedewald JJ, Eustace JA, Rabb H. Acute kidney injury. In: Brenner BM, eds. Brenner and Rector’s The Kidney. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2008:chap 29.
Review Date:
5/30/2011
Reviewed By:
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
