The CKD-EPI 2021 equation estimates glomerular filtration rate (eGFR) from serum creatinine, age and sex. The 2021 refit removed the race coefficient from the 2009 equation and is now the recommended first-line eGFR equation (KDIGO 2024, NKF-ASN task force).
High-yield: CKD staging by eGFR — G1 ≥90 (with other evidence of kidney damage),
G2 60–89, G3a 45–59, G3b 30–44, G4 15–29, G5 <15 ml/min/1.73 m². Drug dosing, contrast decisions
and nephrology referral all key off these bands.
How to use it
Enter creatinine in either unit (converted automatically), the patient's age and sex. The equation applies κ and α constants by sex internally (0.7/−0.241 female, 0.9/−0.302 male) and a ×1.012 factor for females.
Don't miss: creatinine-based eGFR is unreliable at extremes of muscle mass
(amputees, bodybuilders, cachexia, neuromuscular disease) and in acute kidney injury — it assumes
steady state. In those settings use cystatin C or measured clearance. Also: the equation is
validated for adults — pediatric patients need the Schwartz or updated bedside equations.
References
- Inker LA, Eneanya ND, Coresh J, et al. New creatinine- and cystatin C–based equations to estimate GFR without race. N Engl J Med 2021;385:1737–1749.
- Kidney Disease: Improving Global Outcomes (KDIGO) 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int 2024;105(4S):S117–S314.
Draft content — verify against the cited sources before relying on it.