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Cystatin C, Serum Concentration (Quantitative)

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

This test measures the level of cystatin C, a small protein produced by all cells in the body. It helps assess kidney function.

Quick summary

["Cystatin C is a key marker for kidney health and can help track kidney function over time."]

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

Key facts at a glance

LOINC
4997-3
Short code
CMV DNA Tiss Ql Probe
Synonyms
CMV DNA Tiss Ql Probe
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Is Cystatin C?

Cystatin C is a protein that your body produces constantly, regardless of diet or muscle mass. Unlike creatinine, which can vary based on muscle size, cystatin C provides a more consistent measure of kidney function.

Why Is This Test Done?

Doctors may order this test to evaluate kidney function, especially in people with risk factors like diabetes, high blood pressure, or a family history of kidney disease. It’s also useful for monitoring kidney health in patients receiving certain medications or undergoing treatments that affect kidney function.

How Is the Test Performed?

A small blood sample is taken from a vein, usually in your arm. The blood is sent to a lab where it is analyzed to measure cystatin C levels.

What Do Results Mean?

Higher than expected levels may indicate kidney problems, while lower levels may suggest conditions like malnutrition or certain genetic disorders. Your doctor will interpret results in the context of your overall health and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Cystatin C is a reliable marker for kidney function because it is filtered by the kidneys and does not depend on muscle mass or diet. It is often used alongside creatinine to provide a more accurate assessment of kidney health, especially in people with mild to moderate kidney impairment or those with conditions affecting muscle mass.

Short name

Cystatin C

Frequently asked questions

What causes cystatin C levels to change?
Cystatin C levels can be affected by kidney disease, certain medications, infections, or conditions that alter protein production in the body. Chronic kidney disease, dehydration, or severe illness may also influence results.
Is there a difference between cystatin C and creatinine?
Yes. Cystatin C is produced by all cells and is less affected by muscle mass or diet, making it a more consistent measure of kidney function. Creatinine, on the other hand, can vary based on muscle size and diet.
Can food or diet affect cystatin C levels?
No, unlike creatinine, cystatin C levels are not significantly influenced by diet or muscle mass, so fasting is not required for this 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