Background and objectives: Reference values of blood urea nitrogen (BUN), serum creatinine (sCr) and BUN to creatinine ratio (BCR) in the different pediatric populations are not well-established yet. The aim of this study was to determine reference values of BUN, sC and BCR in healthy Iranian children. 

Methods: The study included 3268 children (1670 males and 1598 females) who were hospitalized at Ali-Asghar Children's Hospital (Tehran, Iran) between April 2016 and May 2018. The subjects were stratified into three age groups: toddlers, developing children and adolescents. Demographic data, medical history and laboratory findings were extracted from medical records of the subjects. Statiscal analyses were peformed using SPSS at statistical significance of 0.05.

Results: The mean (95th Percentile) level of BUN was 12.60 mg/dl (range: 6.8 to 20.5 mg/dl). The mean and 95th percentile of sCr was 0.77 mg/dl (range: 0.8 to 1.15 mg/dl). The mean and 95th percentile of BCR was 16 (range: 12.75 to 15.4). The BUN, sCr and BCR levels differed significantly between males and females (P<0.05). In both genders, the concentrations of BUN and sCr were significantly higher in older children (P<0.05). On the contrary, the BCR value decreased significantly with age in both males and females (P<0.05).

Conclusion: This study is the first to report the BUN, sCr, and BCR reference values among healthy Iranian children. These values can be used by clinicians for diagnostic and therapeutic purposes.