Normal BUN and Creatinine Values for an 11-Month-Old Infant
For an 11-month-old infant, normal serum creatinine ranges from 0.2–0.4 mg/dL (18–35 µmol/L) and blood urea nitrogen (BUN) ranges from 5–18 mg/dL. 1
Age-Specific Reference Ranges
Serum creatinine in infants during the first year of life is markedly lower than in older children and adults due to reduced muscle mass and ongoing renal maturation, with typical values of 0.2–0.4 mg/dL (approximately 18–35 µmol/L). 1
BUN values between 5 mg/dL and 18 mg/dL are generally considered acceptable for term infants around 10 months of age. 1
Creatinine levels fall during the neonatal period and then gradually increase with age in both sexes, with full-term infants showing more rapid decline than premature infants. 2
Critical Laboratory Considerations
Assay Method Selection
Enzymatic creatinine assays are strongly recommended for pediatric testing because they provide greater specificity at the low concentrations characteristic of infants. 1
Jaffe-based methods have limited specificity for low creatinine levels in children, with increased interference from non-creatinine chromogens, making them unsuitable for accurate infant measurements. 1
The KDIGO guidelines emphasize that laboratories measuring creatinine in infants or small children must ensure their quality control processes include the lowest end of the expected range of values for this age group. 3
Quality Control Requirements
Laboratory quality-control programs should include verification of performance at the lowest expected infant values to ensure accurate reporting. 1
Enzymatic methods should be used consistently in children given the higher relative contribution of non-creatinine chromogens when using the Jaffe assay, particularly with the high prevalence of icteric and hemolyzed samples in the neonatal period. 3
Clinical Interpretation Framework
Normal Clinical Context
- In a well-appearing, adequately hydrated infant with normal urine output, a serum creatinine of 0.23 mg/dL and BUN of 5 mg/dL are normal and do not require intervention. 1
When to Estimate GFR
When renal function is in question, the bedside Schwartz equation can estimate glomerular filtration rate (eGFR), though validation in children younger than 1 year is limited. 1
The revised Schwartz formula is: eGFR (mL/min/1.73 m²) = 0.413 × (height cm) / (serum creatinine mg/dL). 1
Validated GFR estimating equations should be used rather than relying on serum filtration markers alone. 3
Red Flags Requiring Further Evaluation
Serial laboratory results showing a rising trend in serum creatinine or BUN should prompt a more detailed renal assessment. 1
Additional investigation is warranted if abnormal laboratory trends are accompanied by clinical signs such as oliguria, peripheral edema, hypertension, or failure to thrive. 1
An eGFR level < 90 ml/min per 1.73 m² can be flagged as "low" in children and adolescents over the age of 2 years, though this threshold is not specifically validated for infants under 2 years. 3