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Immunoglobulin G (IgG) Subclass Measurement (Serum)

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

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 and diseases.

Quick summary

["IgG subclasses help assess immune function and identify potential deficiencies or abnormalities."]

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

Key facts at a glance

LOINC
31585-3
Short code
Reticulin IgG Ser Ql
Synonyms
Reticulin IgG Ser Ql
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 recommend this test if you have symptoms of a weakened immune system, such as frequent infections, recurrent ear or sinus infections, or unexplained fatigue. It could also be used to monitor conditions like lupus, rheumatoid arthritis, or other autoimmune diseases where IgG levels might be affected.

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 blood, which usually takes a few minutes. If you’re on blood thinners, let your provider know beforehand.

What the Test Results Mean

IgG subclass levels can vary based on your overall health, age, and medical conditions. Abnormally low or high levels may indicate immune system issues, infections, or certain medical conditions. Your provider will interpret the results in the context of your health history.

Common Conditions Affecting IgG Levels

Low IgG levels may be linked to conditions like common variable immunodeficiency (CVID), HIV/AIDS, or certain autoimmune diseases. High IgG levels can sometimes be seen in chronic infections, certain cancers, or as a reaction to vaccines.

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 change?
IgG subclass levels can change due to infections, immune system disorders (like CVID or autoimmune diseases), aging, medications (such as steroids), or genetic factors. Chronic illnesses, vaccinations, or even stress can also influence these levels.
How often should I get this test?
The frequency of testing depends on your medical condition and symptoms. Your healthcare provider will determine how often you need this test based on your individual needs, such as monitoring immune function or managing a diagnosed condition.
Can diet or lifestyle affect IgG levels?
While diet and lifestyle factors like stress or sleep can impact overall immune function, they do not directly alter IgG subclass levels. However, maintaining a balanced diet and managing stress may support overall immune health.
  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