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Immunoglobulin G (IgG) Subclass Measurement (Serum)

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

This test measures the levels of different types (subclasses) of Immunoglobulin G (IgG), a key part of your immune system. IgG helps fight infections and is important for long-term immunity.

Quick summary

["Understanding your IgG subclass levels helps doctors assess immune function and identify potential deficiencies or immune system issues."]

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

Key facts at a glance

LOINC
107004-4
Short code
T.pallidum Ab.IgG 453 Ser Ql IB
Synonyms
T.pallidum Ab.IgG 453 Ser Ql IB
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ib
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 Is Done

Your doctor may order this test if you have symptoms like frequent infections, low energy, or if you’re at higher risk for infections due to conditions like HIV, cancer, or certain autoimmune diseases. It can also help monitor treatment responses in patients receiving immune-modulating therapies.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm or vein to draw a blood sample. The process usually takes a few minutes, and you may feel a brief pinch. If you’re nervous, let your healthcare provider know.

What the Test Results Mean

IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4). Abnormal levels can indicate immune system problems, such as low immunity or overactive immune responses. Your results will be compared to standard reference ranges provided by your lab.

Common Conditions Linked to IgG Subclass Issues

Low IgG levels may suggest conditions like common variable immunodeficiency (CVID), where the immune system doesn’t produce enough antibodies. High IgG levels could be linked to chronic infections, autoimmune diseases, or certain medications.

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 test results to vary?
IgG levels can change due to age, overall health, medications (like steroids), infections, or immune system conditions. For instance, older adults may naturally have slightly different IgG levels than younger people, and certain treatments (like chemotherapy) can temporarily affect immune function.
How often should I get this test?
Your doctor will determine how often you need this test based on your health history, symptoms, and treatment plan. Some people may need it once a year or more if they have chronic conditions affecting immunity.
Can lifestyle changes affect IgG subclass levels?
Yes, lifestyle factors like diet, stress, and exercise can influence immune function. Eating a balanced diet rich in vitamins (like vitamin D and zinc) and managing stress may support healthy IgG levels, but this test is primarily used for medical evaluation rather than general wellness monitoring.
  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