Skip to content

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

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

This test measures the levels of specific subclasses of Immunoglobulin G (IgG), a type of antibody in your blood. IgG is the most abundant antibody and plays a key role in protecting the body from infections.

Quick summary

["IgG subclasses help identify immune system function and potential deficiencies."]

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

Key facts at a glance

LOINC
48666-2
Short code
IgG.IT Ser+CSF-mCnc
Synonyms
IgG.IT Ser+CSF-mCnc
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

What Does This Test Measure?

IgG is divided into four subclasses (IgG1, IgG2, IgG3, and IgG4), each with distinct roles in immunity. This test evaluates the concentration of these subclasses in your serum or plasma. The results can help assess immune response, identify deficiencies, or evaluate conditions affecting antibody production.

Why Might You Need This Test?

Doctors may order IgG subclass testing if you have recurrent infections, autoimmune diseases, or conditions like common variable immunodeficiency (CVID). It can also be used to monitor treatment responses in patients with immune-related disorders.

How Is the Test Performed?

A blood sample is drawn from a vein, typically in your arm. The blood is then processed to separate serum or plasma for analysis using an immunoassay method, which detects and quantifies the IgG subclasses.

What Do the Results Mean?

Results show the concentration of each IgG subclass. Abnormal levels may indicate immune system dysfunction, such as low levels suggesting immunodeficiency or high levels potentially linked to certain autoimmune conditions. Your healthcare provider will interpret the results in the context of your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG subclass levels

Frequently asked questions

How often will I need this test?
This test is typically ordered as needed, depending on your symptoms, diagnosis, or treatment plan. Your doctor may recommend follow-up tests if initial results suggest an immune-related condition. Regular monitoring may be required for chronic conditions or ongoing treatments.
What are the normal ranges for IgG subclasses?
There are no universally standardized reference ranges for IgG subclasses because they can vary by lab and patient factors. Your results will be compared to ranges specific to your lab and clinical context. Your doctor will discuss what your results mean for you.
Can I prepare for this test?
No special preparation is needed for this blood test. You may have some mild discomfort from the needle, but it usually goes away quickly. If you have a bleeding disorder or take blood thinners, let your doctor know before the 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