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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 protein produced by all cells in the body. It helps assess kidney function.

Quick summary

["A simple blood test to check kidney health."]

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

Key facts at a glance

LOINC
35929-9
Short code
CT Guided Brst-R Loc
Synonyms
CT Guided Brst-R Loc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct
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

Why Is This Test Done?

Your doctor may order a cystatin C test to evaluate kidney function, especially if you have symptoms like fatigue, swelling, or changes in urine output. It’s also useful for monitoring kidney disease progression or planning treatments like dialysis.

How Is the Test Performed?

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

What Do Results Mean?

Higher than expected cystatin C levels may indicate kidney problems, while lower levels could suggest overhydration or other conditions. Your doctor will interpret results in relation to your overall health and medical history.

Common Reasons for Testing

Doctors often use cystatin C alongside other tests (like creatinine) to get a more accurate picture of kidney function, especially in people with diabetes, high blood pressure, or a family history of kidney disease.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Kidney Function Monitoring

Short name

Cystatin C

Frequently asked questions

How often will I need this test?
Your doctor will determine how often you need cystatin C testing based on your medical condition, treatment plan, and kidney function. Some people may need it yearly, while others may need it more or less frequently.
Can I eat or drink before this test?
Typically, no special preparation is needed. However, always follow your doctor’s instructions, as some tests may require fasting or avoiding certain foods/drinks.
Will the test hurt?
The blood draw is usually quick and mild discomfort is normal. Most people feel little to no pain afterward.
  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