Immunoglobulin G (IgG) Subclass Quantification (Serum)
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 bacteria, viruses, and toxins.
["Understanding your IgG subclass levels can help identify immune system function or deficiencies."]
Key facts at a glance
- LOINC
- 40964-9
- Short code
- Deprecated S pneum2 IgG Ser-mCnc
- Synonyms
- Deprecated S pneum2 IgG Ser-mCnc
- 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 recommend this test if you have symptoms like frequent infections, unusual fatigue, or if you have a known immune disorder. It could also be part of an evaluation for conditions like common variable immunodeficiency (CVID) or other antibody-related issues.
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 mass concentration (grams per liter). Lower than expected levels in one or more subclasses may suggest an immune system that doesn’t produce enough antibodies, while higher levels might indicate overactivity or certain autoimmune conditions.
Common Conditions Linked to IgG Subclass Results
Abnormal IgG subclass levels can be linked to conditions like recurrent infections, autoimmune diseases, or certain genetic disorders. For example, low IgG2 levels might be associated with difficulty fighting certain bacteria.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG subclass testing helps diagnose and monitor immune-related disorders, guiding treatment plans such as antibody replacement therapy or immune-modulating medications.
Short name
IgG Subclass Levels
Frequently asked questions
What does it mean if my IgG subclass levels are low?
How often should I get this test?
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