Calculators · Paediatrics & Neonatology · Formula
CKiD U25 eGFR (2021, age- and sex-specific)
Also called CKiD under 25, U25 equation, Pierce eGFR, paediatric cystatin C eGFR
eGFR for ages 1–25 years from height/creatinine and/or cystatin C, with age- and sex-dependent K (CKiD U25).
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Formula and scoring
eGFR = K × height (m) ÷ SCr (mg/dL), or K ÷ cystatin C (mg/L). Creatinine K — male: 39.0 × 1.008^(age−12) for age <12, 39.0 × 1.045^(age−12) for 12–18, 50.8 for ≥18; female: 36.1 × 1.008^(age−12), 36.1 × 1.023^(age−12), 41.4. Cystatin C K — male: 87.2 × 1.011^(age−15) for <15, 87.2 × 0.960^(age−15) for 15–18, 77.1 for ≥18; female: 79.9 × 1.004^(age−12) for <12, 79.9 × 0.974^(age−12) for 12–18, 68.3 for ≥18.
Exam and ward pearls
- Note the units: U25 uses height in metres (K ≈ 40), whereas bedside Schwartz uses centimetres (k = 0.413).
- Bridges paediatric and adult care — one equation from age 1 to 25, avoiding the jump when switching to CKD-EPI.
When not to rely on it
- Developed in children with CKD (median measured GFR about 48); not validated for screening healthy children.
- Internal validation only; the published supplement rounds K to integer ages, so results may differ by a fraction from table-based calculators.
Source
- Pierce CB, Muñoz A, Ng DK, Warady BA, Furth SL, Schwartz GJ. Age- and sex-dependent clinical equations to estimate glomerular filtration rates in children and young adults with chronic kidney disease. Kidney Int. 2021;99(4):948-56. doi:10.1016/j.kint.2020.10.047 · PMID 33301749
Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.