eGFR Calculator for Children

The bedside Schwartz formula (2009), the simplified version that can be worked out quickly at the patient's bedside, estimates the glomerular filtration rate in children and adolescents between 1 and 18 years of age. It is calculated by multiplying 0.413 by height in centimeters and dividing the result by serum creatinine in mg/dL [1]. It uses height instead of age and sex because, in children, muscle mass (the source of creatinine) grows along with height.

Adult formulas such as CKD-EPI were developed and validated in people over 18 years of age. Children have a much smaller and constantly changing muscle mass, so the same creatinine value corresponds to a lower glomerular filtration rate in a 6-year-old than in an adult. Applying an adult formula to a child would give systematically wrong results. From 18 years on you move to the eGFR calculator for adults, which uses CKD-EPI 2021.

As a reference, after the age of 2 a value of about 90 mL/min/1.73 m² or more is considered normal, while persistently lower values may point to reduced kidney function. In children under 2, normal values are naturally lower because the kidney is still maturing. Interpretation rests with the pediatrician, the pediatric diabetologist or the pediatric nephrologist, in the context of the whole assessment.

The result depends on the laboratory method used for creatinine. The formula assumes a standardized IDMS method (isotope dilution mass spectrometry, the international reference method against which creatinine assays are calibrated), used by most modern laboratories. In children with unusual muscle mass (for example neuromuscular disease or malnutrition), the estimate may be inaccurate. The formula does not apply to infants under 1 year of age. An abnormal value is always confirmed by repeat testing and medical assessment.