How to use it
- Choose sex and enter age in years (18 to 120).
- Pick the unit your lab report uses, mg/dL or µmol/L, and enter the serum creatinine.
- Read the eGFR in mL/min/1.73 m² and the GFR category it falls into.
The CKD-EPI 2021 equation
With serum creatinine Scr in mg/dL:
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × 1.012 (if female)
- κ = 0.7 for females and 0.9 for males;
- α = −0.241 for females and −0.302 for males;
- min(Scr/κ, 1) is the smaller of Scr/κ and 1, max(Scr/κ, 1) the larger.
Creatinine in µmol/L is divided by 88.4 first. The category is taken from the eGFR rounded to a whole number:
| eGFR, mL/min/1.73 m² | Category |
|---|---|
| 90 or more | G1 |
| 60–89 | G2 |
| 45–59 | G3a |
| 30–44 | G3b |
| 15–29 | G4 |
| below 15 | G5 |
Worked example
A 60-year-old man with creatinine 1.2 mg/dL: Scr/κ = 1.2 ÷ 0.9 = 1.333, so the min term is 1 and the max term is 1.333^−1.2 = 0.708. The age term is 0.9938^60 = 0.689. eGFR = 142 × 0.708 × 0.689 = 69 mL/min/1.73 m², category G2.
A 50-year-old woman with creatinine 0.7 mg/dL: Scr/κ = 1, so both terms are 1. eGFR = 142 × 0.9938^50 × 1.012 = 142 × 0.733 × 1.012 = 105, category G1.
Limits and common mistakes
- This is an estimate for information, not a diagnosis. A doctor reads it together with urine tests, history and earlier results.
- Creatinine depends on muscle mass and diet. Very muscular people, amputees, people with very low muscle mass and people on a high-meat diet can get misleading estimates.
- The equation assumes stable kidney function. During acute kidney injury creatinine lags behind and the eGFR overstates filtration.
- Mixing up units is the most common error: 1.0 entered as µmol/L instead of mg/dL gives an impossible result. Check the unit on the lab report.