Results

Results of the blood urea nitrogen test are measured in milligrams per deciliter (mg/dL) in the United States and in millimoles per liter (mmol/L) internationally. In general, around 7 to 20 mg/dL (2.5 to 7.1 mmol/L) is considered normal.

But normal ranges may vary, depending on the reference range used by the lab, and your age. Ask your doctor to explain your results.

Urea nitrogen levels tend to increase with age. Infants have lower levels than other people do, and the range in children varies.

Generally, a high blood urea nitrogen level means your kidneys aren't working well. But elevated blood urea nitrogen can also be due to:

  • Urinary tract obstruction
  • Congestive heart failure or recent heart attack
  • Gastrointestinal bleeding
  • Dehydration, resulting from not drinking enough fluids or for other reasons
  • Shock
  • Severe burns
  • Certain medications, such as some antibiotics
  • A high-protein diet

If kidney damage is a concern, ask your doctor what factors may be contributing to the damage and what steps you can take to try to control them.

July 02, 2016
References
  1. Blood urea nitrogen (BUN), serum. Mayo Medical Laboratories. http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/81793. Accessed May 9, 2016.
  2. Rodwell VW, et al., eds. Catabolism of Proteins & of Amino Acid Nitrogen. In: Harper's Illustrated Biochemistry. 30th ed. New York, N.Y.: McGraw-Hill Education; 2015. http://www.accessmedicine.com. Accessed May 10, 2016.
  3. Blood urea nitrogen. Lab Tests Online. https://labtestsonline.org/understanding/analytes/bun/tab/test/. Accessed May 10, 2016.
  4. Inkler LA, et al. Assessment of kidney function. http://www.uptodate.com/home. Accessed May 9, 2016.

Blood urea nitrogen (BUN) test