eGFR Calculator (CKD-EPI 2009)

eGFR by CKD-EPI 2021: estimated glomerular filtration rate

eGFR (estimated glomerular filtration rate) is the standard marker for staging chronic kidney disease (CKD). The CKD-EPI 2021 equation (NEJM, Inker et al.) removed the race coefficient that the 2009 version carried. Using serum creatinine (Scr, mg/dL) and sex-specific constants k (0.7 for women, 0.9 for men) and α (−0.241 for women, −0.302 for men): eGFR = 142 · min(Scr/k, 1)^α · max(Scr/k, 1)^(−1.200) · 0.9938^age · (1.012 if female). The result is in mL/min/1.73 m². KDIGO stages: G1 ≥90 (normal); G2 60–89 (mildly reduced); G3a 45–59; G3b 30–44; G4 15–29 (severe); G5 <15 (kidney failure, dialysis range). Example: a 60-year-old man with Scr 1.0 mg/dL has eGFR ≈ 90 mL/min/1.73 m² (G2).

Clinical context

eGFR is computed automatically by most labs from creatinine and is used to screen for CKD in diabetes, hypertension, and routine geriatric care. It guides renal dose adjustment of medications (vancomycin, gabapentin, DOACs, contrast media), triggers nephrology referral typically at G3b or below, and informs the indication for dialysis at G5 with uremic symptoms. Persistence of reduced eGFR for ≥3 months (combined with albuminuria) defines CKD. Acute changes in creatinine make eGFR unreliable in AKI — use raw creatinine trends instead.

FAQ

Why was race removed in 2021? The race coefficient was empirical, not biological, and inflated eGFR in Black patients, delaying CKD diagnosis and transplant listing. The 2021 equation performs comparably across populations without it.

When is eGFR unreliable? Extremes of muscle mass (amputees, body builders, sarcopenia), acute kidney injury, pregnancy, and unusual diets (creatine supplementation, high-meat intake) all distort creatinine. Consider cystatin C-based equations in these cases.

Why is the value normalized to 1.73 m²? It is the average adult body surface area; normalization allows comparison across body sizes. For drug dosing in extreme body sizes, de-index by multiplying back by actual BSA/1.73.

CKD-EPI or MDRD? CKD-EPI 2021 is more accurate at near-normal GFR (>60) and is recommended by KDIGO 2024. MDRD systematically underestimates in healthy individuals.