Blood Urea Nitrogen (BUN), Serum/Plasma


Urea is a major by-product of protein metabolism; urea is synthesised in the liver from ammonia as a result of deamination of amino acids. 90% of produced urea is freely filtered by the glomeruli of the kidneys. However, a large portion (40-70%) is passively reabsorbed from the renal tubules. Urea (and BUN) concentration in the blood can vary with diet, hepatic function, and numerous disease states.


BUN was the first endogenous substance measured in serum or plasma to assess renal function. Urea or BUN is frequently requested along with creatinine to aid in the differential diagnosis of pre-renal (cardiac compensation, water depletion or increased catabolism), renal (acute glomerulonephritis, chronic nephritis, polycystic kidney, nephrosclerosis and tubular necrosis) and post-renal(urinary tract obstruction) hyperuremia.

Sample Type, Quantity & Conditions

1 ml Serum 1 ml K2-EDTA or Li-Heparin Plasma Stability: 7 Days at 15-25 °C 7 Days at 2-8 °C 1 Year at (-15)-(-25) °C

Special Precautions

Normal Range

Adults: 6-23 mg/dL 2.14-8.21 mmol/L Infants (< 1 Year): 4-19 mg/dL 1.43-6.78 mmol/L Children: 5-18 mg/dL 1.79-6.43 mmol/L

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