Glomerular Filtration Rate (GFR / CKD-EPI) Calculator
Calculate estimated Glomerular Filtration Rate (eGFR) and Chronic Kidney Disease (CKD) stages using the official 2021 CKD-EPI race-free creatinine consensus equation.
# Calculation Pipeline (Chain of Thought)
- Step 1 (Constants Selection): Females:
κ = 0.7, α = -0.241, multiplier = 1.012; Males: κ = 0.9, α = -0.302, multiplier = 1.000. - Step 2 (CKD-EPI 2021 Race-Free Equation):
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^-1.200 × 0.9938^Age × Multiplier. - Step 3 (KDIGO Stage Categorization): G1 (≥90), G2 (60-89), G3a (45-59), G3b (30-44), G4 (15-29), G5 (<15 mL/min/1.73m²).
- Step 4 (Albuminuria Cross-Reference): Evaluate Urine Albumin-to-Creatinine Ratio (uACR): A1 (<30 mg/g), A2 (30-300 mg/g), A3 (>300 mg/g).
Decision Rule: Nephrology Benchmark: An eGFR consistently < 60 mL/min/1.73m² for >3 months defines Chronic Kidney Disease regardless of kidney damage markers.
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| CKD-EPI 2021 RACE-FREE eGFR ARCHITECTURE |
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[ Serum Creatinine (mg/dL) ] + [ Age ] + [ Biological Sex (M/F) ]
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[ NKF-ASN 2021 Race-Free Equation: 142 * min(Scr/k,1)^a * max(Scr/k,1)^-1.2 * 0.9938^Age ]
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[ ESTIMATED GLOMERULAR FILTRATION RATE (eGFR) ]
(mL/min/1.73 m² surface)
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Stage 1 (≥90) Stage 2 (60-89) Stage 3 (30-59)
Normal / Optimal Mild Decline Moderate CKD (3a/3b)
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Stage 4 (15-29) Stage 5 (<15) [ + uACR Screen ]
Severe CKD Kidney Failure (ESRD) A1 (<30), A2 (30-300), A3 (>300)
Frequently Asked Questions
Why did the 2021 CKD-EPI equation eliminate race from the calculation?
In 2021, the National Kidney Foundation (NKF) and American Society of Nephrology (ASN) established the race-free CKD-EPI equation to eliminate race-based clinical disparities and standardize kidney diagnosis objectively.
What are the 5 clinical stages of Chronic Kidney Disease (CKD)?
Stage 1: eGFR ≥ 90 (Normal with kidney damage/proteinuria). Stage 2: eGFR 60–89 (Mild decrease). Stage 3a: eGFR 45–59 (Mild-moderate). Stage 3b: eGFR 30–44 (Moderate-severe). Stage 4: eGFR 15–29 (Severe). Stage 5: eGFR < 15 (Kidney failure / End-Stage Renal Disease).
How do muscle mass and creatine supplements skew serum creatinine?
Creatinine is a metabolic byproduct of muscle creatine breakdown. Highly muscular lifters and individuals taking creatine supplements produce more creatinine, which can artificially lower calculated eGFR despite perfectly healthy kidneys.
When is Cystatin C testing recommended for kidney function confirmation?
Cystatin C is an alternative blood filtration marker produced by all nucleated cells that is independent of muscle mass and diet. It is used to confirm true kidney function when creatinine-based eGFR is borderline.
Renal Function & Diagnostic Checklists
- Pre-Lab Blood Draw Preparation: Avoid heavy resistance workouts and avoid consuming cooked red meat for 24 hours prior to blood testing. Strenuous exercise elevates transient serum creatinine.
- Hydration Standardization: Dehydration causes transient pre-renal azotemia, elevating blood urea nitrogen (BUN) and creatinine. Ensure baseline hydration before routine blood work.
- Blood Pressure Target (<120/80 mmHg): Strict blood pressure management is the #1 intervention to halt CKD progression. Target resting blood pressure under 120/80 mmHg under physician guidance.
- Confirmatory Cystatin C Testing: If your creatinine eGFR falls between 45 and 59 without proteinuria, request a serum Cystatin C test to calculate eGFRcr-cys for definitive confirmation.