What Is a Normal Cystatin C Level?
Normal ranges: Cystatin C 0.52–0.98 mg/L; eGFR (cystatin C) 90 or above (60–89 is mildly decreased). Values outside these ranges may point to a condition that needs further evaluation.
Reference Range Table
| Marker | Low | Normal | High |
|---|---|---|---|
| Cystatin C | Below 0.52 mg/L — rarely a concern | 0.52–0.98 mg/L | Above 0.98 mg/L — kidneys may be filtering less |
| eGFR (cystatin C) | Below 60 for 3+ months — chronic kidney disease range | 90 or above (60–89 is mildly decreased) | — |
What Affects Your Results
High-dose corticosteroids, thyroid disease (an overactive thyroid raises cystatin C, an underactive one lowers it), smoking, inflammation and obesity can shift results somewhat. Unlike creatinine, a large meat meal or heavy exercise before the draw has little effect.
When to Retest
If eGFR is below 60, it is usually confirmed with a repeat test after about 3 months, since chronic kidney disease is defined by a lasting decrease. People with diabetes or high blood pressure are commonly checked at least once a year.
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