Blood Urea Nitrogen, BUN



Quest Diagnostics Test Code: 294

Urea is the principle waste product of protein catabolism. BUN is most commonly measured in the diagnosis and treatment of certain renal and metabolic diseases.

Blood urea nitrogen is a test that measures level of urea in blood. Urea is a final product of protein catabolism. It is produced in the liver in sequence of chemical reactions called the urea cycle, in which ammonia is transformed to urea. Ammonia (in a form of urea) is excreted from the body by kidneys. Since the liver is the main organ to produce urea, and kidneys are responsible for its excretion, elevated BUN level in blood could be a sign of liver or kidney malfunction. If elevated BUN level is accompanied by elevated liver enzymes (AST, ALT), decreased level of plasma proteins and severe coagulopathy, it could lead the doctor to diagnosis of liver failure. On the other hand, if elevated BUN level is accompanied by reduced level of urine (compromised urination) or increased level of creatinine, it it most probably the sign of kidney failure. Reference range for urea level is 3-7 mmol/l. Level of urea could be also measured in urine.

This test is performed in following conditions such as:

• Indications of kidney damage
• Kidney function needs to be evaluated
• Need help to determine the effectiveness of dialysis treatment if you are receiving haemodialysis or peritoneal dialysis
• Need to check your liver function, urinary tract obstruction or gastrointestinal bleeding, although elevated BUN level does not confirm any of these conditions

Also Known As: Urea


Specimen Collected
  • Blood
Estimated Time Taken

Turnaround time for the Urea Nitrogen test (BUN test) is typically 1 business day.