Cystatin C
Cystatin C is a small protein produced at a constant rate by all nucleated cells in the body. It is freely filtered by the kidneys and almost completely reabsorbed and degraded in the proximal tubules. Unlike creatinine, cystatin C production is independent of muscle mass, diet, and sex.
Why it matters: Cystatin C is a more accurate marker of kidney function than creatinine in many populations — particularly in elderly patients, those with low muscle mass, vegetarians, and people with higher body mass index. Cystatin C-based eGFR is often used when creatinine-based eGFR may be unreliable. It can flag kidney decline earlier than creatinine.
May increase with:
May decrease with:
What is Cystatin C?
Cystatin C is a small protein produced at a constant rate by all nucleated cells in the body. It is freely filtered by the kidneys and almost completely reabsorbed and degraded in the proximal tubules. Unlike creatinine, cystatin C production is independent of muscle mass, diet, and sex.
What might a high or low Cystatin C mean?
Cystatin C is a more accurate marker of kidney function than creatinine in many populations — particularly in elderly patients, those with low muscle mass, vegetarians, and people with higher body mass index. Cystatin C-based eGFR is often used when creatinine-based eGFR may be unreliable. It can flag kidney decline earlier than creatinine.
What is the typical reference range for Cystatin C?
The general-population reference range shown here is 0.51 – 0.98 mg/L. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.
What can affect Cystatin C?
It may be higher with: Declining kidney function (any cause), Corticosteroid therapy (increases production), Hyperthyroidism, Active inflammation, Obesity (modestly). It may be lower with: Improved kidney function, Hypothyroidism.
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