Cystatin C
Cystatin C is a protein produced by all nucleated cells that is filtered by the kidneys. It is used as an alternative to creatinine for estimating kidney function.
Category: Kidney Function
Also known as: cystatin c, cystatin-c, cys c, serum cystatin c, cistatin c
Reference range: 0.62–1.15 mg/L (Source: ABIM)
Standard unit: mg/L
High values may indicate
High cystatin C levels may indicate decreased kidney function, chronic kidney disease, or acute kidney injury.
Low values may indicate
Low cystatin C levels are uncommon and generally not clinically significant, though they may be seen with hyperthyroidism or corticosteroid use.
Frequently asked questions
- What is a normal Cystatin C level?
- A typical reference range for Cystatin C is 0.62–1.15 mg/L (source: ABIM). Reference ranges vary by laboratory, age, and sex, so always compare against the range on your own lab report.
- What units is Cystatin C measured in?
- Cystatin C is most commonly reported in mg/L. Labs in different countries may use other units — you can convert between them with BloodId's blood test unit converter.
- Where do Cystatin C reference ranges come from?
- BloodId uses ABIM standard reference ranges and educational information from MedlinePlus (see our methodology). Reference ranges still vary by lab, age, and sex, so always compare against your own report.
- Can I track Cystatin C over time?
- Yes. Upload results from any lab and BloodId charts your Cystatin C over time against its reference range, so you can see whether the trend is rising, falling, or stable.
Related biomarkers
Source: MedlinePlus, U.S. National Library of Medicine
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