C4C (Cystatin C) Serum/plasma Mass Concentration
This test measures the amount of cystatin C, a protein produced by nearly all cells in your body, in your blood. It helps assess kidney function.
["Cystatin C supports kidney health and may help detect early kidney problems."]
Key facts at a glance
- LOINC
- 4500-5
- Short code
- C4CH50CSF
- Synonyms
- C4 CH50 CSF-mCnc
- Category
- chemistry
- Sample
- csf
- Container
- Sterile CSF collection tube (polypropylene), tube 2 or 3 preferred for chemistry analysis
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Nephelometry
- CPT
- 86161
- SNOMED
- 44608007
- Specimen volume
- 1-2 mL of cerebrospinal fluid
- Stability
- Stable for 2 hours at room temperature; 24 hours refrigerated at 2-8°C; 1 month frozen at -20°C or below. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 200
- TAT
- 24–72 hours
- Order
- routine
Why This Test Is Done
Your doctor may order a cystatin C test to evaluate kidney function, especially if you have symptoms like swelling, fatigue, or changes in urine. It can also be used alongside other tests to monitor kidney health in people with diabetes, high blood pressure, or a family history of kidney disease. Some doctors use it instead of or in addition to creatinine tests to better assess kidney function, particularly in people with low muscle mass or certain medical conditions.
How the Test Works
A small blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it is analyzed to measure cystatin C levels. This protein is stable in blood and doesn’t depend on muscle mass or diet, unlike creatinine.
What to Expect Before the Test
No special preparation is needed for this test. You can eat and drink normally on the day of your visit. If you’re on certain medications, let your doctor know, as they may affect your results.
What to Expect After the Test
You may feel slight discomfort or bruising at the injection site, but it should go away quickly. Avoid heavy lifting or strenuous activity for a few hours afterward to prevent bleeding.
Reference range
Reference ranges for CSF complement C4 CH50 are not well established and vary by laboratory; typically reported qualitatively or with assay-specific valuesN/A
No special preparation required. Lumbar puncture should be performed under sterile conditions by a qualified healthcare provider.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Cystatin C Blood Test
Frequently asked questions
What Does a High or Low Level Mean?
How Does It Compare to Other Kidney Tests?
Can I Fast Before This Test?
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