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Cystatin C, Serum Concentration

Published: August 9, 2026Updated: August 16, 2026

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.

Quick summary

["Cystatin C helps evaluate how well your kidneys are working."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
16711-4
Short code
Cys+(Hcys)2 Ur Ql
Synonyms
Cys+(Hcys)2 Ur Ql
Category
chemistry
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Doctors may order a cystatin C test to check for kidney problems, especially if you have symptoms like swelling in your legs, fatigue, or changes in urine output. It can also be used alongside other tests to monitor kidney function in people with diabetes, high blood pressure, or other health conditions that affect the kidneys.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The blood is sent to a lab where it’s analyzed to measure cystatin C levels. No special preparation is needed, but you may be asked to fast for a few hours before the test if instructed by your healthcare provider.

What Do Results Mean?

Higher than expected cystatin C levels may suggest kidney damage or disease, while lower levels might indicate less kidney function. Your doctor will compare your results with your medical history and other tests to determine if further action is needed.

Common Reasons for Testing

Cystatin C is often used in combination with creatinine to estimate glomerular filtration rate (GFR), a measure of kidney function. It’s also helpful for monitoring kidney health in people who have conditions like chronic kidney disease or those taking medications that can affect kidney function.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Cystatin C

Frequently asked questions

How long will it take to get my results?
Results are typically available within a few days to a week, depending on your lab’s processing schedule. Your doctor will contact you once they have the results and explain what they mean for your health.
Can I eat or drink before the test?
Most of the time, you can eat and drink normally before the test unless your doctor or lab instructions specify otherwise. Some labs may ask for fasting, so always follow their guidance.
Is there any risk or discomfort with this test?
There’s usually mild discomfort when the needle is inserted, but it’s over quickly. Rarely, some people might feel a slight bruise or swelling at the injection site. If you’re concerned, talk to your doctor before the test.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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