Cystatin C
Cystatin C is a blood marker measured to estimate how well the kidneys are filtering and clearing small proteins from the bloodstream. On a Cystatin C on a blood test, the value is reported as a concentration and is often used with other lab values to give a broader picture of body chemistry. A Cystatin C test result can vary with age, muscle mass, and other factors, so the Cystatin C reference range depends on the lab method.
What Is Cystatin C?
Cystatin C is a small protein found in the blood that is measured on a Cystatin C on a lab report as a marker of kidney filtering. It is made by many cells in the body and released at a fairly steady rate, so the Cystatin C test reflects how efficiently it is cleared from the bloodstream. On a Cystatin C on a blood test, the result is usually reported as a concentration, not a percent or cell count. The Cystatin C normal range is set by each laboratory using its own method.
Why Is Cystatin C Tested?
A Cystatin C test is commonly ordered in a Kidney Panel, and it may also appear with other chemistry tests that assess overall blood chemistry. The Cystatin C test helps add context when comparing filtration markers and can be reviewed alongside creatinine and blood urea nitrogen (BUN). In routine screening, a Cystatin C test result helps build a broader picture of how the blood is being filtered and cleared. The full name, Cystatin C, is often reported with the abbreviation Cystatin C on the lab report.
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Cystatin C Normal Range
| Group | Range | Unit |
|---|---|---|
| Adult Male | 0.6–1 | mg/L |
| Adult Female | 0.6–1 | mg/L |
Reference ranges may vary by laboratory and individual factors.
What Does High Cystatin C Mean?
High Cystatin C generally means more of the protein is staying in the blood than expected, which can reflect reduced clearance by the kidneys. In many labs, a Cystatin C test result above about 1.0 to 1.2 mg/L is considered high Cystatin C, though the Cystatin C normal range varies by method. High Cystatin C on a lab report is often interpreted together with creatinine and estimated filtration values to understand the overall pattern. The exact meaning depends on the Cystatin C reference range used by the laboratory.
Associated factors
What Does Low Cystatin C Mean?
Low Cystatin C means less of the protein is measured in the blood than the lab expects. A Cystatin C test result below the Cystatin C normal range may reflect increased clearance or lower production from body tissues. Low Cystatin C on a blood test is less commonly emphasized than high Cystatin C, and the exact interpretation depends on the laboratory’s Cystatin C reference range. The result is most useful when read with other kidney-related markers and the rest of the panel.
Associated factors
How Cystatin C Relates to Other Values
Cystatin C is often read with creatinine, blood urea nitrogen (BUN), and estimated filtration values from the same Kidney Panel. When Cystatin C and creatinine move in the same direction, that pattern usually points to a broader change in blood clearance rather than a one-marker shift. Creatinine is influenced more by muscle mass, while Cystatin C is less tied to muscle, so the two together can give a more balanced view. On a lab report, Cystatin C may also be compared with urinalysis markers when a fuller blood-and-urine picture is available.
What Factors Affect Cystatin C Levels?
Age, body composition, and smoking can shift Cystatin C a little even when the overall health picture is stable. Hydration status and recent exercise can cause short-term movement in a Cystatin C test result, especially when values are near the Cystatin C reference range. Pregnancy and thyroid hormone changes can also affect the number seen on a Cystatin C on a blood test. Different laboratory methods may use slightly different Cystatin C normal range cutoffs, so one lab’s result may not match another’s exactly. Time of day and recent fluid intake can add small day-to-day variation.
How It Is Tested
Cystatin C is measured from a blood draw, usually from a vein in the arm. The lab analyzes the sample for the concentration of Cystatin C, and results are commonly reported in mg/L. The Cystatin C test is an immunoassay-based measurement on most platforms.
How to Prepare
No fasting is usually required for a Cystatin C test. The sample is typically collected as part of a routine blood draw in a Kidney Panel.
Frequently Asked Questions
What is a normal Cystatin C level?
What does Cystatin C stand for?
What does a high Cystatin C mean on a lab report?
What does a low Cystatin C mean on a lab report?
Can hydration affect Cystatin C?
What is the difference between Cystatin C and creatinine?
What unit is Cystatin C measured in?
How much can Cystatin C change between tests?
Is Cystatin C different for men and women?
Why is Cystatin C tested in a Kidney Panel?
Disclaimer
This content is for informational and educational purposes only. It is not intended as medical advice, diagnosis, or treatment recommendation. Reference ranges may vary by laboratory. Always discuss your results with a qualified healthcare professional.
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