Synonym
Urea nitrogen, BUN
Plasma
Urine
Fluid
Adult patient:
Heparin gel tube
Minimum blood volume: 5 mL
Spot urine:
Plain bottle
Minimum volume: 10 mL
24 Hr urine:
Plain bottle
Minimum volume: 10 mL
Paediatric patient:
Paediatric heparin tube
Number of vials: 1
Minimum blood volume: 1.3 mL
Authorisation code required
No
24 Hr available service
Yes
(Call extension: 3353 for express result)
Spot urine: Yes
24 Hr urine: No
No
Method
Spectrophotometry
Reference interval
Plasma:
| Female: | 2.6 - 6.6 mmol/L |
| Male: | 3.1 - 7.8 mmol/L |
(Source: from local population study in 2008)
24 Hr urine: 428 - 714 mmol/d
The urinary excretion of urea (BUN) varies significantly with dietary intake. The values given are typical of subjects on average diet.
Clinical indication
Plasma:
Investigation of renal function
Urine:
Urine urea is only occasionally of value in the assessment of nitrogen balance in patients receiving parenteral nutrition, or in selected patients with non-oliguric acute or chronic renal failure.
Urine urea may also be of value on a random specimen, in the presence of oliguria, to assess renal function.
Result interpretation
Plasma:
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.
Urine:
Urea excretion is largely dependent on protein intake, tissue breakdown and renal function.
Measurement of uncertainty
Frequency of measurement
Daily