Understanding the 2021 CKD-EPI eGFR Equation and Adult Kidney Filtration Stages
Learn how laboratories estimate glomerular filtration rate (eGFR) from serum creatinine in adults aged 18+, why the 2021 race-free equation was adopted, and why eGFR is always paired with urine albumin (uACR).
How the 2021 Race-Free CKD-EPI Creatinine Equation Works
In 2021, the National Kidney Foundation (NKF) and American Society of Nephrology (ASN) Task Force recommended adopting the refit 2021 CKD-EPI creatinine equation (Inker et al., NEJM 2021), which estimates adult GFR from standardized serum creatinine, age, and sex without a race coefficient.
The equation is validated for adults aged 18 years and older in steady-state kidney function. If serum creatinine is reported in µmol/L, it is converted to mg/dL by dividing by 88.4.
| KDIGO GFR Category | eGFR (mL/min/1.73m²) | Clinical Description (Requires >=3 Months Persistence) |
|---|---|---|
| G1 | >= 90 | Normal or high (not CKD unless kidney damage markers such as uACR >=30 mg/g are present) |
| G2 | 60 – 89 | Mildly decreased (not CKD unless kidney damage markers are present) |
| G3a | 45 – 59 | Mildly to moderately decreased |
| G3b | 30 – 44 | Moderately to severely decreased |
| G4 | 15 – 29 | Severely decreased |
| G5 | < 15 | Kidney failure |
Limitations and When to Seek Medical Care
- The 2021 CKD-EPI equation does not apply to children or adolescents under age 18, pregnant individuals, or acute kidney injury.
- Consult a clinician to interpret serum creatinine alongside cystatin C, urine albumin-to-creatinine ratio (uACR), and longitudinal trends.
Related Calculators
eGFR Calculator (2021 CKD-EPI Race-Free Equation)
Estimate kidney filtration rate in adults aged 18 years and older using the 2021 CKD-EPI race-free creatinine equation recommended by the National Kidney Foundation (NKF) and American Society of Nephrology (ASN).
Urine Albumin-to-Creatinine Ratio (uACR) Calculator
Normalize spot urine albumin and urine creatinine lab units into the standardized Urine Albumin-to-Creatinine Ratio (uACR) in both mg/g and mg/mmol, and view KDIGO A1, A2, and A3 albuminuria categories.
Blood Pressure Calculator (Category, Pulse Pressure & MAP)
Classify an adult blood pressure reading against the 2017 ACC/AHA adult reference table and calculate Pulse Pressure (PP) and estimated Mean Arterial Pressure (MAP) in mmHg.
Frequently Asked Questions
Does an eGFR of 72 mL/min/1.73m² automatically mean chronic kidney disease?
No. In KDIGO guidelines, an eGFR of 60–89 mL/min/1.73m² (G2) without albuminuria or other structural/functional kidney damage markers is not classified as chronic kidney disease.
Sources and Review Information
- [S13] Inker LA, Eneanya ND, Coresh J, et al. New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race (2021 CKD-EPI). N Engl J Med. 2021;385(19):1737-1749. Reference Source
- [S14] KDIGO / National Kidney Foundation. Urine Albumin-to-Creatinine Ratio (uACR) Albuminuria Categories in CKD (A1 <30, A2 30-300, A3 >300 mg/g). Reference Source
Prepared by: GlucoBP Editorial & Engineering Team · Verification status: Formula verified against published reference; clinical review pending · Last updated: 2026-11-15