Immunoglobulin G (IgG) Subclass Measurement (Serum)
This test measures the levels of specific 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.
["Understanding your IgG subclass levels can help identify immune system function or deficiencies."]
Key facts at a glance
- LOINC
- 40925-0
- Short code
- Deprecated S pneum9 IgG sp2 Ser IA-mCnc
- Synonyms
- Deprecated S pneum9 IgG sp2 Ser IA-mCnc
- Category
- coagulation
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ia
- 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 recommend this test if you have symptoms like frequent infections, autoimmune conditions, or if you’re being evaluated for immune-related disorders. It may also be used to monitor treatment responses in certain conditions.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if serum/plasma is required. Bring any medications or supplements you’re taking to discuss with your provider.
What the Test Involves
A blood sample will be taken from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause significant discomfort. The sample is sent to a lab for analysis of IgG subclass concentrations.
What the Results Mean
Results show the mass concentration of IgG subclasses (IgG1, IgG2, IgG3, IgG4) in your blood. While reference ranges vary by lab, abnormal levels may indicate immune system issues, such as hypogammaglobulinemia or certain autoimmune diseases.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG subclass testing is critical for diagnosing or managing conditions like chronic infections, immunodeficiency disorders, or autoimmune diseases. Low levels of certain subclasses may suggest impaired immune function, while elevated levels could indicate conditions like multiple myeloma or certain inflammatory diseases.
Short name
IgG Subclass Levels
Frequently asked questions
What does an abnormal IgG subclass result mean?
How often should I get this test?
Can lifestyle changes 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