BLOOD UREA NITROGEN

BLOOD UREA NITROGEN - serum

Application: Investigation of renal function.

 
Explanation:  In the liver, amino acids (from protein digestion) are catabolized and ammonia is formed.  The ammonia is combined to form urea, which is transported to the kidneys for excretion.  BUN is directly related to the metabolic function of the liver and the excretory function of the kidney. 
   

Increased levels are seen with reduced glomerular filtration due to renal or pre-renal disease; bleeding into the gastrointestinal tract; hypercatabolic states. Reduced values are seen in pregnancy; with water retention; with reduced synthesis as a result of decreased protein intake, severe liver disease, or urea-cycle defects.
   

Patients with increased BUN are said to have azotemia.

Specimen: 5 ml blood in red- or green-top tube.


Reference Interval:

Neonate:
1.0-4.0 mEq/L
Adult:
3.0-8.0 mEq/L