BUN Level of 4.7 mg/dL in a 1-Month-Old Infant
A BUN level of 4.7 mg/dL is normal and appropriate for a 1-month-old infant, requiring no intervention or further evaluation in the absence of other clinical concerns.
Normal Reference Range Context
Pediatric BUN values are physiologically lower than adult values, particularly in infants, due to their lower muscle mass, higher total body water percentage, and different protein metabolism compared to adults 1
The typical normal BUN range for infants is approximately 5-18 mg/dL, though values slightly below 5 mg/dL can be entirely normal in the first months of life, especially in breastfed infants with lower protein intake 1
A BUN of 4.7 mg/dL falls within or just below the lower end of normal and does not indicate any pathology in a 1-month-old infant 1
Clinical Significance
Low-normal BUN values in infants reflect appropriate physiology, not disease states, as infants have:
- Lower muscle mass generating less creatinine and urea
- Higher metabolic rates with efficient protein utilization
- Breast milk or formula providing appropriate but not excessive protein loads 1
Pathologically low BUN (below 2-3 mg/dL) would require severe malnutrition or liver failure, neither of which is suggested by a value of 4.7 mg/dL 2
When to Be Concerned
BUN elevation above 18-20 mg/dL in infants warrants evaluation for dehydration, though BUN alone is not reliable for assessing hydration status in children with gastroenteritis 1
Signs requiring further evaluation include:
Common Pitfalls to Avoid
Do not assume low-normal BUN indicates malnutrition or inadequate feeding in an otherwise thriving infant, as this is physiologically appropriate 1
Do not use BUN as a sole marker of hydration status in pediatric patients, as 88% of dehydrated children with metabolic acidosis had normal BUN values in one study 1
Avoid comparing infant BUN values directly to adult reference ranges, which typically show 7-20 mg/dL as normal but are not applicable to the pediatric population 5