A protein marker of kidney filtration, more accurate than creatinine alone.
Cystatin C is a small protein made by all the cells in your body at a steady rate. The kidneys filter it out of the blood, so the level reflects how well they are filtering.
Unlike creatinine, cystatin C barely depends on muscle mass, age, or sex, which makes it a useful and often more accurate marker of kidney function.
A high cystatin C points to reduced kidney filtration. Because it does not depend on muscle, it can pick up early kidney decline that creatinine misses, especially in older adults or people with low or high muscle mass.
It is used to estimate filtration rate (eGFR), either on its own or combined with creatinine for a more precise result. A low level is not a concern.
Aniva reads your result against research-backed ranges, not just the lab's wide normal. The reference shown below is specific to this biomarker.
| Group | Serum cystatin C (SI) |
| Adults | ~0.6 to 1.0 mg/L |
| Note | rises gradually with age |
Ranges are guidance only and vary by lab and assay. The result is most useful turned into a cystatin C based eGFR. Read your result against your own lab's reference interval, in line with DGKL practice.
High dose steroids and an over or underactive thyroid can shift cystatin C. Unlike creatinine, it is largely unaffected by muscle mass, diet, and exercise, which is one of its advantages. Smoking and obesity can raise it slightly.
Best read with creatinine and eGFR. A combined creatinine and cystatin C eGFR is the most accurate estimate of kidney function.
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