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Immunoglobulin G (IgG) Subclass Quantification (Serum/Plasma)

Published: August 9, 2026Updated: August 16, 2026

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 infections and regulate immune responses.

Quick summary

["IgG subclasses play a critical role in your body’s immune defense system."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
96476-7
Short code
IgLON5 IgG Ser Ql IF
Synonyms
IgLON5 IgG Ser Ql IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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 can also help diagnose or monitor conditions affecting antibody function, such as certain immunodeficiencies or antibody-mediated diseases.

What to Expect Before the Test

No special preparation is needed for this blood test. You may be asked to fast for 8–12 hours before your blood draw if your provider specifies it, but this is not always required for IgG subclass testing. Bring a list of medications to your appointment.

During the Test

A healthcare professional will insert a small needle into your arm to draw a blood sample. The process usually takes a few minutes. You may feel a brief pinch, but most people tolerate it well. The blood is then sent to a lab for analysis.

What the Results Mean

Results show the concentration of IgG1, IgG2, IgG3, and IgG4 subclasses. Abnormal levels may indicate immune system dysfunction, such as low antibody production (hypogammaglobulinemia) or excessive antibody activity (e.g., in autoimmune diseases). Your provider will interpret the results in the context of your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG subclass levels

Frequently asked questions

What causes IgG subclass levels to be abnormal?
Abnormal IgG subclass levels can result from conditions like primary immunodeficiency diseases (e.g., selective IgA deficiency), autoimmune disorders (e.g., rheumatoid arthritis), chronic infections, or certain medications that affect antibody production. Rarely, genetic factors or liver/kidney disease may also influence these levels.
How often should I get this test?
The frequency depends on your health condition. If you have a known immune disorder, your provider may recommend regular monitoring. Otherwise, this test is typically ordered as needed for diagnosis or management of suspected immune-related issues.
Can diet or lifestyle affect IgG subclass results?
While diet and lifestyle factors (like vitamin deficiencies or chronic stress) can impact overall immune function, they generally do not directly alter IgG subclass levels in blood tests. Follow your provider’s advice on any specific preparations or lifestyle considerations for your test.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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