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Blood Urea Nitrogen
Abbreviation: BUN
Panel: Metabolic, Kidney & Electrolytes · All metabolic & kidney tests
Typical adult reference range
| Conventional units | 7–20 mg/dL |
| SI units | 2.5–7.1 mmol/L |
Ranges vary between laboratories and methods — compare your result with the range printed on your own report.
What a high or low result can mean
High blood urea nitrogen: high values can be seen in reduced kidney function, dehydration, and high protein intake.
Low blood urea nitrogen: low values may occur with low protein intake, overhydration, or severe liver disease.
These are associations, not a diagnosis: the same result can have several causes, and your clinician interprets it with the rest of your results and history.
Good to know
SI value is expressed as urea.
◆ Kidney note
This test is closely tied to kidney health, and it is one a kidney specialist (nephrologist) watches closely. On this site, kidney-related results are a special focus: see the kidney and dialysis medicines in our Drug Guide and the kidney condition hubs for the wider picture.