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What is eGFR and why does it matter?
eGFR (estimated glomerular filtration rate) is a core measure of how much blood the kidneys filter and clean each minute; its unit is mL/min/1.73m². The kidneys filter waste and excess fluid from the blood; when this capacity drops, waste builds up. Because eGFR is hard to measure directly, it is estimated from creatinine, which is easily measured in the blood, together with age and sex. It is the most widely used indicator for staging and monitoring chronic kidney disease.
How is eGFR calculated?
This tool uses the current, race-free CKD-EPI 2021 creatinine equation (the race coefficient was removed in 2021). The equation is computed from the creatinine/κ ratio with sex-specific exponents:
κ = female 0.7 · male 0.9
α = female −0.241 · male −0.302
Scr = serum creatinine (mg/dL)
Example: a 55-year-old man with a creatinine of 1.1 mg/dL:
Scr/κ = 1.1 ÷ 0.9 = 1.22 → eGFR ≈ 79 mL/min/1.73m²
Since this value is in the 60–89 range, it corresponds to KDIGO G2 (mildly decreased).
Method: CKD-EPI Creatinine 2021 race-free equation (Inker LA et al., N Engl J Med, 2021). Staging: KDIGO GFR categories (G1 ≥90, G2 60–89, G3a 45–59, G3b 30–44, G4 15–29, G5 <15). Unit conversion: 1 mg/dL = 88.4 µmol/L.
What to know when interpreting eGFR
- A single value is not a diagnosis: Diagnosing chronic kidney disease requires the impairment to last at least 3 months and/or additional findings such as albumin in the urine.
- Muscle mass matters: Because creatinine is produced by muscle, eGFR can be misleading in people with very high or very low muscle mass.
- Acute situations: The equation is valid for stable (steady) creatinine; it does not reflect the rapidly changing values seen in acute kidney injury.
- For adults: CKD-EPI 2021 is validated for ages 18 and over; different equations (e.g. Schwartz) are used in children.
Frequently Asked Questions
In healthy adults, eGFR is usually 90 mL/min/1.73m² or above (KDIGO G1). A value of 60–89 (G2) on its own, with no additional findings, is often consistent with normal aging. If it stays below 60 for three months, it should be evaluated for kidney disease.
Older equations included a coefficient for race, which could lead to inequity. The updated CKD-EPI equation published in 2021 removed this coefficient; it now uses only creatinine, age and sex. This tool uses the current equation.
Just select µmol/L as the unit; the tool converts it automatically. If you want to convert by hand: mg/dL = µmol/L ÷ 88.4. For example, 97 µmol/L ≈ 1.1 mg/dL.
A single low value is not a definitive diagnosis. Chronic kidney disease requires the reduction to last at least 3 months and/or additional findings such as albumin in the urine or damage on imaging. Always review the result with your physician.
Very high or very low muscle mass, excessive meat intake, some medications, pregnancy and acute illness can affect creatinine and therefore the eGFR estimate. In these cases a physician may use other methods (e.g. cystatin C).
Controlling blood pressure and blood sugar, staying well hydrated, and reducing salt and unnecessary painkiller use support kidney health. In advanced stages, protein and mineral intake is adjusted with a physician/dietitian. Consult your health care team for a personal plan.