Immunoglobulin G (IgG) Subclass Measurement (Serum/Plasma)
This test measures the levels of different subclasses of Immunoglobulin G (IgG), a key antibody protein in your immune system. IgG subclasses help protect against infections and play roles in immune responses.
["IgG subclasses help identify immune system function and potential deficiencies."]
Key facts at a glance
- LOINC
- 55974-0
- Short code
- IgG Ser ID-mCnc
- Synonyms
- IgG Ser ID-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- immune-diffusion
- CPT
- 82784
- 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 Might Be Ordered
Your healthcare provider may order this test if they suspect an immune system disorder, such as a deficiency in certain IgG subclasses, or to monitor conditions like chronic infections, autoimmune diseases, or after certain treatments like chemotherapy. It can also be used to check for immune responses to vaccines.
What to Expect Before the Test
No special preparation is needed for this test. You may have a blood draw, where a small amount of blood is taken from a vein in your arm. If you’re on blood thinners, let your provider know before the test.
What the Test Results Mean
IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4). Abnormal levels of any subclass may indicate immune dysfunction, such as poor infection control, autoimmune issues, or certain genetic disorders. Your results will be compared to standard reference ranges for your age and health status.
Common Conditions Monitored
This test is often used to diagnose or monitor conditions like common variable immunodeficiency (CVID), recurrent infections, or immune-related side effects from treatments like cancer therapy.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG subclasses have distinct roles in immunity. For example, IgG2 is important for bacterial infections, while IgG3 is involved in immune responses to toxins. Low levels of specific subclasses may point to weakened immune defense mechanisms, while high levels could suggest overactive immune responses or certain autoimmune conditions. Your provider will interpret results in the context of your overall health and symptoms.
Short name
IgG Subclass Levels
Frequently asked questions
What causes IgG subclass levels to be checked?
How long does it take to get test results?
Can diet or lifestyle affect IgG subclass 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 16, 2026. · Read our editorial policy