Calculate eGFR from Cystatin C
Use this tool to estimate glomerular filtration rate (eGFR) using the CKD-EPI 2012 cystatin C equation.
What this cystatin C GFR calculator does
This calculator estimates kidney function using cystatin C, a blood biomarker that can help assess filtration more reliably in some situations than creatinine alone. It outputs an estimated GFR in mL/min/1.73 m² and a CKD G-stage category.
Equation used (CKD-EPI 2012 cystatin C)
The formula applied is:
eGFR = 133 × min(Scys/0.8, 1)-0.499 × max(Scys/0.8, 1)-1.328 × 0.996Age × (0.932 if female)
Where Scys is serum cystatin C in mg/L.
How to interpret the result
Your estimated GFR is grouped into kidney function stages:
| GFR Category | eGFR (mL/min/1.73 m²) | General Interpretation |
|---|---|---|
| G1 | ≥ 90 | Normal or high (if other kidney markers are normal) |
| G2 | 60-89 | Mildly decreased |
| G3a | 45-59 | Mild to moderate decrease |
| G3b | 30-44 | Moderate to severe decrease |
| G4 | 15-29 | Severely decreased |
| G5 | < 15 | Kidney failure range |
Why use cystatin C?
- Less influenced by muscle mass than creatinine.
- Useful when creatinine-based eGFR may be misleading (low muscle mass, frailty, unusual body composition).
- Often used to confirm CKD staging when creatinine estimates are borderline.
Important limitations
Lab method matters
Cystatin C should ideally be measured with standardized assays. Different methods can produce slightly different results.
Clinical context still matters
Inflammation, thyroid disease, corticosteroids, and other factors may affect cystatin C. Your clinician may combine cystatin C with creatinine and urine testing for a more complete assessment.
Not for dialysis dosing decisions on its own
Medication and treatment decisions may require additional equations, trends, and direct clinical judgment.
Practical tips before using this calculator
- Use the exact value from your lab report and confirm units are mg/L.
- Check the date of testing and compare trends over time.
- Pair eGFR with urine albumin-to-creatinine ratio (UACR) for better risk stratification.
Medical disclaimer
This calculator is educational and not a substitute for professional medical advice, diagnosis, or treatment. Always discuss your results with a qualified healthcare professional, especially if you have diabetes, hypertension, known kidney disease, or abnormal lab findings.