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 slices · age and sex · 1 source
Filed under panels: Renal Function , Metabolic Panel · topics: Metabolic , Renal
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.
Population Distribution
Browse by Demographic
| Age (years) | male (mg/dL) | female (mg/dL) |
|---|---|---|
| 20-29 | 8–20 (13) | 7–17 (11) |
| 30-39 | 8–21 (13.2) | 7–18 (11) |
| 40-49 | 10–22 (15) | 7–19 (12) |
| 50-59 | 9–25 (15) | 8–22 (14) |
| 60-69 | 10–25 (17) | 9–26 (16) |
| 70+ | 12–32 (18) | 10–32 (18) |
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.