Immunoglobulin G (IgG) Subclass 1, 2, 3, or 4 Quantification (Serum)
This test measures specific types of Immunoglobulin G (IgG), a key antibody protein in your blood. IgG helps fight infections and is divided into subclasses (IgG1, IgG2, IgG3, IgG4) that play different roles in immunity.
["Understanding your IgG subclass levels can help identify immune system function or deficiencies."]
Key facts at a glance
- LOINC
- 109983-7
- Short code
- IgLON5 IgG Msmt Ser
- Synonyms
- IgLON5 IgG Msmt Ser
- Category
- chemistry
- 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 conditions, or if they suspect an immune disorder. It may also be used to monitor treatment responses in certain conditions, such as chronic infections or immune-related diseases.
What to Expect Before the Test
No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw a blood sample. If you’re on blood thinners, let your provider know before the test.
What the Test Results Mean
IgG subclasses are measured in arbitrary units or mass concentration. Abnormal levels can indicate immune system issues, such as low immunity (hypogammaglobulinemia) or overactive immune responses. Your provider will interpret results in the context of your health and symptoms.
Common Conditions Linked to IgG Subclass Levels
Low IgG subclass levels may be linked to recurrent infections, autoimmune diseases, or conditions like common variable immunodeficiency (CVID). High levels might suggest chronic infections, certain cancers, or overactive immune responses.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG subclass testing helps diagnose and manage conditions where specific antibody types are critical. For example, low IgG2 levels may indicate trouble fighting certain bacterial infections, while elevated IgG4 could be associated with autoimmune diseases or allergic reactions. This test supports personalized treatment planning for immune-related disorders.
Short name
IgG subclass levels
Frequently asked questions
What does a low IgG subclass mean?
How are IgG subclass results used in treatment?
Can diet or supplements 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