CKD-EPI 2021 eGFR (Creatinine)
The CKD-EPI 2021 equation estimates glomerular filtration rate from serum creatinine, age, and sex using the race-free 2021 formula. It is the current recommended equation for eGFR calculation in adults worldwide, replacing the 2009 equation that included a race coefficient.
inputs
✓ when to use
Use for all adult patients (≥18 years) requiring kidney function assessment: CKD detection and staging, drug dosing guidance, pre-operative assessment, cardiovascular risk stratification, and monitoring of nephrotoxic medications. Should be reported by laboratories automatically with every serum creatinine measurement.
✗ when not to use
eGFR from creatinine is unreliable in conditions that alter creatinine generation independently of GFR: extremes of muscle mass (bodybuilders, amputees, muscle-wasting diseases), acute kidney injury (creatinine has not yet reached steady state), pregnancy, and very high or low dietary protein intake. In these situations, consider cystatin C-based eGFR (CKD-EPI 2021 cystatin C equation) or measured GFR. Not validated in children (<18) — use Schwartz equation. For drug dosing, some labels specify Cockcroft-Gault CrCl rather than CKD-EPI eGFR — check the drug monograph.
clinical pearls
- The 2021 equation is race-free. Race was removed because it is a social construct that does not reliably predict biological differences in creatinine metabolism, and its inclusion perpetuated health disparities. Do not use the older 2009 equation with race coefficient.
- eGFR is an ESTIMATE. It is most accurate at lower GFR values and less precise at higher values. Laboratories typically report '>90' rather than an exact number above 90. Never make major clinical decisions based on small eGFR changes within the >60 range.
- For drug dosing, check whether the drug label specifies CKD-EPI eGFR or Cockcroft-Gault CrCl. Many older drug labels were developed using CrCl (which uses actual body weight and is not normalised to BSA), and the two methods can give meaningfully different results, especially in extremes of body weight.
- CKD diagnosis requires persistence — a single low eGFR does not diagnose CKD. Repeat testing at ≥3 months is needed to confirm chronicity. Acute drops in eGFR should be investigated as AKI.
- Always pair eGFR with urine albumin-creatinine ratio (uACR). The KDIGO heat map uses both eGFR and albuminuria to classify CKD risk. A patient with eGFR 65 and uACR 300 mg/g is at much higher risk than one with eGFR 40 and uACR <30 mg/g.