Cystatin C, Serum Concentration (Quantitative)
This test measures the concentration of cystatin C, a protein produced by all cells in the body that helps regulate kidney function.
["Cystatin C is often used to assess kidney health and monitor kidney disease progression."]
Key facts at a glance
- LOINC
- 42394-7
- Short code
- CT Pulm system W 133Xe IH
- Synonyms
- CT Pulm system W 133Xe IH
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ct
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order this test to evaluate kidney function, especially if you have symptoms like fatigue, swelling, or changes in urine output. It can also help monitor kidney disease, especially in people with diabetes or high blood pressure, or those taking medications that affect kidney function. Some doctors use it as an alternative to blood urea nitrogen (BUN) and creatinine tests, as cystatin C levels may provide additional information about kidney health, particularly in certain populations.
How Is the Test Performed?
A blood sample is drawn from a vein, usually in your arm. The blood is then sent to a lab for analysis. The test measures the amount of cystatin C protein in your serum (liquid part of blood). The results are typically available within a few days.
What Do the Results Mean?
Higher than expected cystatin C levels may indicate reduced kidney function. Lower levels might suggest other conditions, but this is less common. Your doctor will compare your results with your medical history and other tests to interpret the meaning. Reference ranges can vary slightly by lab, so always discuss your results with your healthcare provider.
Possible Causes of Abnormal Results
Elevated cystatin C levels can be due to kidney disease, including chronic kidney disease (CKD), acute kidney injury, or other conditions affecting kidney function. It may also be influenced by factors like age, muscle mass, or certain medications. Low levels are less frequently associated with specific conditions and may require further evaluation by your doctor.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
Cystatin C
Frequently asked questions
What questions might you have about this test?
Can I eat or drink anything before this test? Typically, you can eat and drink normally unless your doctor instructs otherwise. Some tests may have specific fasting requirements, but cystatin C tests do not.
Will this test affect my treatment? Sometimes, cystatin C levels help guide treatment decisions, especially for kidney-related conditions. Your doctor will discuss any changes to your care plan based on the results.
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy