Immunoglobulin G (IgG) Subclass Measurement (Serum)
This test measures the levels of different subclasses of Immunoglobulin G (IgG), a type of antibody in your blood. IgG is the most common antibody and plays a key role in fighting infections.
["Understanding your IgG subclass levels can help identify immune system function and potential deficiencies."]
Key facts at a glance
- LOINC
- 47505-3
- Short code
- Deprecated S pneum6 IgG Ser-mCnc
- Synonyms
- Deprecated S pneum6 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, recurrent ear or sinus infections, or if you’ve been diagnosed with a condition affecting your immune system, such as HIV, lupus, or certain autoimmune diseases. 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 needed for this test. You’ll typically provide a blood sample drawn from a vein in your arm. If you’re on blood thinners, let your provider know before the test to avoid unnecessary bleeding.
What the Results Mean
IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4), each with different roles in immunity. Abnormal levels of any subclass can indicate immune system issues, such as low immunity (hypogammaglobulinemia) or overactivity. Your results will be compared to standard reference ranges provided by your lab.
Common Conditions Linked to IgG Subclass Abnormalities
Low levels of certain IgG subclasses are often linked to recurrent infections, poor wound healing, or chronic inflammatory conditions. High levels of IgG3, for example, may be associated with autoimmune diseases or certain allergic reactions. Always discuss your results with your healthcare provider.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
IgG Subclass Levels
Frequently asked questions
What questions might you have about this test?
How long will it take to get my results? Results are typically available within 1 to 3 business days, depending on your lab’s processing time.
What if my IgG subclass levels are outside the normal range? If your results are abnormal, your provider will discuss potential causes and next steps, such as further testing or treatment adjustments.
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