Glomerular Filtration Rate (GFR) Calculator | HealthCalculum
Estimate kidney function using CKD-EPI or MDRD formulas
Important Medical Disclaimer
This calculator is an educational and clinical decision support tool. Results DO NOT replace professional medical evaluation, laboratory tests, or clinical judgment. Always consult a qualified healthcare professional for diagnosis, treatment, and clinical decisions. Calculations are based on scientifically validated formulas but may not be applicable to all patients.
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What is GFR?
Glomerular Filtration Rate (GFR) estimates kidney function by measuring how efficiently kidneys filter waste from blood. It classifies chronic kidney disease (CKD) stages from 1 (normal) to 5 (kidney failure).
How to Calculate
Enter serum creatinine level, age, gender, and race. Choose CKD-EPI (recommended) or MDRD formula. The calculator estimates GFR and classifies CKD stage based on kidney function level.
CKD Stages
Stage 1: GFR ≥90
Normal or high kidney function
Stage 2: GFR 60-89
Mildly decreased kidney function
Stage 3: GFR 30-59
Moderately decreased kidney function
Stage 4: GFR 15-29
Severely decreased kidney function
Stage 5: GFR <15
Kidney failure - dialysis or transplant needed
Limitations
GFR estimates are affected by muscle mass, diet, medications, and acute illness. CKD-EPI is more accurate than MDRD, especially at higher GFR values. Clinical diagnosis requires additional tests and assessment by nephrologist.
Frequently Asked Questions
Which formula should I use: CKD-EPI or MDRD?
CKD-EPI is more accurate and current, especially for GFR >60. It's recommended as the current standard. MDRD tends to underestimate GFR at higher values.
What does each CKD stage mean?
Stages 1-2: normal/mildly decreased function (monitoring). Stage 3: moderate loss (intervention needed). Stage 4: severe loss (prepare for renal therapy). Stage 5: failure (dialysis/transplant).
Does muscle mass affect estimated GFR?
Yes. Creatinine is a product of muscle metabolism. Very muscular people may have higher creatinine without kidney disease. People with low muscle mass may have falsely low values.
How often should I check my GFR?
Depends on CKD stage. Stages 1-2: annually. Stage 3: 6-12 months. Stages 4-5: 3-6 months or as directed by nephrologist. Conditions like diabetes require more frequent monitoring.
Scientific References
- 1. Levey AS, Stevens LA, Schmid CH, et al. A new equation to estimate glomerular filtration rate. Ann Intern Med. 2009;150(9):604-612.
- 2. National Kidney Foundation. K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Am J Kidney Dis. 2002;39(2 Suppl 1):S1-266.
- 3. Inker LA, Eneanya ND, Coresh J, et al. New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race. N Engl J Med. 2021;385(19):1737-1749.
- 4. Levey AS, Bosch JP, Lewis JB, Greene T, Rogers N, Roth D. A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Ann Intern Med. 1999;130(6):461-470.