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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, which helps assess kidney function.

Quick summary

["A simple blood test to check kidney health using a protein that stays stable throughout the body."]

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

Key facts at a glance

LOINC
107075-4
Short code
cyCD79a cells NFr Spec FC
Synonyms
cyCD79a cells NFr Spec FC
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
flow-cytometry
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 This Test Matters

Cystatin C is useful because it doesn’t change with hydration levels like other kidney function tests (such as creatinine), making it a reliable marker for kidney function, especially in people with chronic kidney disease or those who may not drink enough water.

How the Test Works

Your blood sample is collected and analyzed using an immunoassay method to measure cystatin C levels. This test is typically done on serum (liquid part of blood after clotting).

What to Expect Before the Test

No special preparation is needed for this test. You may have a light snack or drink as usual, but avoid heavy meals before your appointment. If you’re on certain medications or have a history of kidney issues, let your healthcare provider know.

What the Results Mean

Higher than expected cystatin C levels may indicate kidney problems, including reduced kidney function. Lower levels might suggest overhydration or other conditions. Your healthcare provider will interpret results in relation to your overall health and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Cystatin C

Frequently asked questions

What could cause elevated cystatin C levels?
Elevated cystatin C can be caused by kidney disease, dehydration, or certain medications. It can also be influenced by age, muscle mass, and overall health. Chronic kidney disease is the most common reason for elevated levels, but it can also be seen in conditions affecting other organs.
How often should I get this test?
Your healthcare provider will determine how often you need this test based on your medical history, symptoms, and overall health. For example, people with kidney disease may need regular monitoring, while others might only need it occasionally.
Can diet or lifestyle affect cystatin C levels?
While diet and lifestyle factors like hydration and muscle mass can indirectly influence kidney function, cystatin C itself is not directly affected by diet. However, maintaining good kidney health through hydration, a balanced diet, and avoiding excessive toxins can support normal kidney function.
  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