Cystatin C, Serum Concentration
This test measures the level of cystatin C, a protein produced by all cells in the body that helps regulate cell growth and division. It’s often used to assess kidney function.
["Cystatin C helps evaluate how well your kidneys are working."]
Key facts at a glance
- LOINC
- 82539-8
- Short code
- CASHEW IgE
- Synonyms
- Cashew nut (rAna o) 3 IgE Qn
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) - red-top or gold-top tube
- Units
- N/A
- Ref low
- 0
- Ref high
- 0.35
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–150 years
- Method
- Immunoassay (Fluorescent Enzyme Immunoassay - FEIA, e.g., ImmunoCAP)
- CPT
- 86003
- SNOMED
- 395128004
- Specimen volume
- 0.5 mL serum (minimum); 1 mL preferred
- Stability
- Room temperature: 7 days; Refrigerated (2-8°C): 14 days; Frozen (-20°C or below): 1 year. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order this test to check for kidney problems, including early-stage kidney disease. It can also help monitor kidney function in people with diabetes, high blood pressure, or other health conditions that affect the kidneys.
How Is the Sample Collected?
A small amount of blood is drawn from a vein in your arm by a healthcare professional. The blood is placed in a tube and sent to the lab for testing.
What Do the Results Mean?
Higher than expected levels of cystatin C may suggest kidney problems, while lower levels might indicate other conditions. Your doctor will interpret the results in relation to your overall health and medical history.
What Are Possible Causes of Abnormal Results?
Elevated cystatin C levels can be linked to kidney disease, dehydration, or certain medications. Lower levels might be seen in conditions like overhydration or certain genetic factors. Always discuss any concerns with your doctor.
Reference range
<0.35 kU/L: Negative; 0.35-0.69 kU/L: Low/Equivocal; 0.70-3.49 kU/L: Moderate; 3.50-17.49 kU/L: High; 17.50-49.99 kU/L: Very High; 50.00-99.99 kU/L: Very High; >=100 kU/L: Very HighN/A
No fasting required. Patient should avoid taking antihistamines for 5-7 days prior to testing if skin prick testing is also planned; however, antihistamines do not typically interfere with serum specific IgE testing. Inform clinician of any recent allergic reactions or immunotherapy.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Cystatin C is a reliable marker for kidney function because it doesn’t depend on kidney filtration rates like creatinine. It’s often used alongside other tests to get a more accurate picture of kidney health, especially in people with diabetes or other chronic conditions.
Short name
Cystatin C
Frequently asked questions
Why might my doctor have ordered this test?
Is there anything I should do before the test?
Can cystatin C levels change with diet or exercise?
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