Cystatin C, Serum Concentration
This test measures the level of cystatin C, a protein produced by all cells in your body. It helps assess your kidneys' function and can be useful in monitoring chronic kidney disease.
["Cystatin C helps evaluate kidney health and may be used alongside other tests to track kidney function over time."]
Key facts at a glance
- LOINC
- 21573-1
- Short code
- CDT
- Synonyms
- CDT Disialo/Tf MFr SerPl
- Category
- chemistry
- Sample
- serum
- Container
- Red-top serum tube (no anticoagulant) or serum separator tube (SST)
- Units
- N/A
- Ref low
- 1.7
- Ref high
- 2
- Critical range
- — – 2 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Capillary electrophoresis or HPLC (High-Performance Liquid Chromatography) for carbohydrate-deficient transferrin (CDT) isoform separation; results expressed as disialo-transferrin to total transferrin ratio
- CPT
- 82373
- SNOMED
- 395145001
- Specimen volume
- 1-2 mL of serum (minimum 0.5 mL)
- Stability
- Serum stable for 7 days at 2-8°C; for longer storage, freeze at -20°C or below for up to 6 months. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 100
- Lipemia max
- 100
- Icterus max
- 50
- TAT
- 24–72 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order a cystatin C test to check for kidney problems, especially if you have risk factors like high blood pressure, diabetes, or a family history of kidney disease. It can also be used to monitor kidney function in people with chronic conditions or after certain treatments.
How Is the Test Performed?
A small blood sample is taken from a vein in your arm. The sample is sent to a lab where it is analyzed to measure cystatin C levels. No special preparation is usually needed, but you may be asked to avoid certain medications or foods for a short time before testing.
What Do Results Mean?
Higher than expected cystatin C levels may indicate kidney problems, while lower levels might suggest other health conditions. Your results will be compared to standard ranges provided by your healthcare team to determine if further action is needed.
Common Reasons for Testing
Cystatin C is often used in combination with creatinine to calculate a more accurate estimate of kidney function, especially in people with low muscle mass or certain medications that affect creatinine levels.
Reference range
Disialo-transferrin / Total transferrin ratio: <1.7% (normal/non-abuser); 1.7-2.0% (gray zone/equivocal); >2.0% (elevated, suggestive of chronic alcohol abuse or congenital disorders of glycosylation)N/A
No fasting required. Patient should abstain from alcohol for at least 2 weeks prior to testing for accurate interpretation. Recent acute alcohol intake may not significantly elevate CDT (reflects chronic consumption pattern).
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Cystatin C
Frequently asked questions
How long does it take to get results?
What does a high cystatin C level mean?
Can diet or medications affect cystatin C levels?
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