Kidney function education
Cystatin C eGFR Calculator: CKD-EPI 2012
Estimate indexed adult GFR from cystatin C, age and sex with the 2012 CKD-EPI cystatin C-only equation.
Cystatin C can be influenced by non-GFR factors including thyroid disease, corticosteroids and inflammation. For adults with stable kidney function; not a pediatric or acute kidney injury equation. A disagreement between markers deserves investigation.
Method and equation
Scys is standardized cystatin C in mg/L and A is age in years. The formula uses 0.8 mg/L as its knot and applies different exponents above and below that concentration; f is 0.932 for the female term and 1 for the male term. This is the 2012 single-marker equation, not the 2021 combined creatinine–cystatin C equation.
eGFR = 133 × min(Scys/0.8, 1)^−0.499 × max(Scys/0.8, 1)^−1.328 × 0.996^A × f
How to use this tool
- Enter a laboratory cystatin C result in mg/L, age and the sex term used by the published equation. Compare it with creatinine-based and combined estimates when those are available.
- Review the original report, earlier results and relevant urine tests with a qualified clinician before making a care decision.
Worked example
A 60-year-old man with cystatin C 1.1 mg/L has an estimated GFR of about 68.5 mL/min/1.73 m². With the same inputs, the female term gives about 63.9.
Understanding the result
The result is normalized to a body surface area of 1.73 m². Cystatin C is less dependent on muscle mass than creatinine; a combined estimate often improves precision when both markers are available, particularly near a clinical decision threshold.
Limitations and safety
- Cystatin C can be influenced by non-GFR factors including thyroid disease, corticosteroids and inflammation. For adults with stable kidney function; not a pediatric or acute kidney injury equation. A disagreement between markers deserves investigation.
- Educational use only. A result cannot diagnose disease or choose a medicine dose. Do not delay urgent care for symptoms or rapidly changing kidney results.
Sources
Method and explanations checked against the sources below on October 14, 2026. This is editorial and technical verification, not a physician review. External sources may be in English.