Cystatin C, Serum Concentration (Quantitative)
This test measures the level of cystatin C, a protein produced by all nucleated cells in your body. It’s often used to assess kidney function.
["Cystatin C helps evaluate kidney health and may be useful in diagnosing or monitoring kidney disease."]
Key facts at a glance
- LOINC
- 99439-2
- Short code
- ANAo3G4
- Synonyms
- Cashew nut (rAna o) 3 IgG4-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or red-top vacutainer tube; serum aliquot tube acceptable
- Units
- N/A
- Ref low
- 0
- Ref high
- 0.1
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Immunoassay (Fluorescent Enzyme Immunoassay / FEIA or Chemiluminescent Immunoassay / CLIA) using recombinant cashew nut allergen component rAna o 3
- CPT
- 86001
- SNOMED
- 116655003
- Specimen volume
- 0.5-1 mL serum (minimum 0.3 mL)
- Stability
- Stable for 7 days at 2-8°C; stable for up to 30 days at -20°C or lower for long-term storage. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 40
- TAT
- 24–72 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order this test to check how well your kidneys are working. High levels can indicate kidney problems, including chronic kidney disease (CKD). It may also be used alongside other tests to monitor kidney function over time, especially in people with diabetes or high blood pressure.
What Does the Test Involve?
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 in your serum (liquid part of blood).
What Are Common Results?
Results are typically reported as a concentration value (e.g., mg/L). While reference ranges vary by lab, higher than expected levels may suggest kidney issues, while lower levels may indicate other conditions or lab errors.
What Does It Mean If My Results Are Abnormal?
If your cystatin C level is elevated, it may signal kidney problems, such as reduced kidney function or glomerulonephritis. Your doctor will discuss this with you and may recommend further testing or adjustments to your treatment plan.
Reference range
Reference ranges are laboratory-specific and method-dependent. Generally reported as negative (<0.10 kU/L or <0.35 mg/L), equivocal/borderline, or positive. Results are typically interpreted alongside clinical history and total IgG4 measurements.N/A
No special preparation required. Patient does not need to fast prior to specimen collection. It is recommended that the patient avoid antihistamine use immediately before specimen collection only if accompanying skin testing is planned. Patients on immunosuppressive therapy may have altered IgG4 levels and results should be interpreted with caution.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
Cystatin C
Frequently asked questions
How often will I need this test?
What if I have kidney disease?
Can I eat or drink anything before the 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 15, 2026. · Read our editorial policy