Immunoglobulin G (IgG) Subclass Measurement (Serum)
This test measures the levels of different subclasses of Immunoglobulin G (IgG), a key antibody protein in your blood that helps fight infections.
["IgG subclasses play a role in immune response and can be checked if you have symptoms of immune system issues or certain conditions."]
Key facts at a glance
- LOINC
- 63375-0
- Short code
- cCP IgA+IgG Ser Ql
- Synonyms
- cCP IgA+IgG Ser Ql
- Category
- coagulation
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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 you have symptoms like frequent infections, autoimmune diseases, or if you’re being evaluated for conditions that affect antibody production, such as HIV, lymphoma, or certain immune deficiencies. It may also be used to monitor treatment responses in patients with immune-related disorders.
What to Expect Before the Test
No special preparation is usually needed. You may have a small needle inserted into a vein in your arm to draw blood. If you’re on blood thinners, let your provider know before the test.
What the Results Mean
IgG is the most abundant antibody in your blood, but measuring its subclasses helps identify specific immune system imbalances. For example, low levels of certain subclasses might indicate immune dysfunction, while high levels could suggest chronic inflammation or autoimmune activity.
Common Conditions Linked to IgG Subclass Levels
Abnormal IgG subclass levels can be linked to conditions like chronic infections, certain cancers (e.g., multiple myeloma), or autoimmune diseases (e.g., rheumatoid arthritis). Your provider will interpret results in the context of your overall health and symptoms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG subclasses are part of the immune system’s defense. IgG1, IgG2, IgG3, and IgG4 each have distinct roles in fighting pathogens, responding to vaccines, and regulating inflammation. Abnormalities may require further testing or treatment adjustments.
Short name
IgG Subclass Levels
Frequently asked questions
How long will I need to wait for my results?
Can I eat or drink before this test?
What if my IgG subclass levels are out of the expected range?
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