Blood Urea Nitrogen (BUN)
Blood urea nitrogen rises gradually with age in the population, reflecting changing renal function, hydration status, protein metabolism, and chronic disease burden.
Unit: mg/dL · 12 groups · age and sex · 1 source
Filed under panels: Renal Function , Metabolic Panel · topics: Metabolic , Renal
Blood Urea Nitrogen (BUN) by age and sex
| Age (years) | Males (mg/dL) | Females (mg/dL) |
|---|---|---|
| 20-29 | median 13 middle 90% 8 to 20 | median 11 middle 90% 7 to 17 |
| 30-39 | median 13 middle 90% 8 to 21 | median 11 middle 90% 7 to 19 |
| 40-49 | median 15 middle 90% 10 to 21.4 | median 12 middle 90% 7 to 19 |
| 50-59 | median 15 middle 90% 9 to 25 | median 14 middle 90% 8 to 22 |
| 60-69 | median 16 middle 90% 10 to 25 | median 16 middle 90% 9 to 27 |
| 70+ | median 18 middle 90% 12 to 32 | median 18 middle 90% 10 to 31.3 |
Download Blood Urea Nitrogen (BUN) percentiles (CSV) Values at full stored precision; tables on this site may round for display. Licensed under CC BY 4.0.
Population Distribution
Blood urea nitrogen (BUN) reflects the concentration of urea nitrogen in serum and is influenced by protein intake, liver urea production, hydration status, and kidney function. These NHANES percentiles describe the full US population rather than a screened healthy subgroup. Note: 1 mg/dL BUN is approximately 0.357 mmol/L urea.
Frequently Asked Questions
Why does BUN rise with age?
Population BUN drifts upward with age because renal function declines, comorbidity accumulates, dehydration becomes more common, and catabolic stress is more frequent in older adults.
Is BUN the same as urea?
Not exactly. BUN reports only the nitrogen portion of urea. Laboratories outside the US often report urea directly in mmol/L rather than BUN in mg/dL.
How do I convert BUN to urea mmol/L?
Multiply by 0.357. For example, 14 mg/dL BUN is approximately 5.0 mmol/L urea.
Data Sources
Cite this data
LabNorms. Blood Urea Nitrogen (BUN) population percentiles by age and sex. Data: NHANES 2017-March 2020 Pre-Pandemic. https://labnorms.com/analytes/bun/. Licensed under CC BY 4.0. Accessed [date].
Download Blood Urea Nitrogen (BUN) percentiles (CSV) Values at full stored precision; tables on this site may round for display. Licensed under CC BY 4.0.