An alternative kidney function marker, less affected by muscle mass than creatinine.
What is it
Cystatin C is a protein produced by all nucleated cells and cleared by the kidneys. Unlike creatinine, it is less influenced by muscle mass.
Why it's measured
Cystatin C has been studied as a more accurate kidney function marker in specific populations in published research.
Reference range
Standard laboratory reference
0.5 – 1.0 mg/L
Reference ranges vary by laboratory. Your individual reference range will appear on your test report and should be interpreted by your physician in the context of your overall health profile.
What results may indicate
Elevated
Has been associated with reduced kidney function in research literature.
Lower
Generally considered favorable.
These associations are general. They are not a personal diagnosis or prediction. Discuss your individual results with your physician in the context of your full health profile.
When it's measured
Used when creatinine-based eGFR may be inaccurate (very high or low muscle mass, athletes).
Related markers
Measured in
A complete look at your heart, hormones, metabolism, inflammation, and longevity systems — drawn at Quest or LabCorp, reviewed by a U.S.-licensed physician.
Explore the Apex Panel →This information is for general educational purposes only and is not medical advice. Lab results alone are not intended to diagnose, treat, or cure any condition and do not replace the advice of a healthcare provider. OPTML does not offer medical advice, a diagnosis, medical treatment, or any form of medical opinion.