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

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

This test measures specific types of antibodies called immunoglobulin G (IgG) subclasses in your blood. IgG is the most common antibody in your immune system and helps fight infections.

Quick summary

["IgG subclasses play a key role in your body’s immune response, and their levels can provide insight into how your immune system is functioning."]

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

Key facts at a glance

LOINC
85993-4
Short code
S pneum Da 14 IgG Ser-aCnc
Synonyms
S pneum Da 14 IgG Ser-aCnc
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

What Does This Test Measure?

IgG antibodies are divided into four main subclasses: IgG1, IgG2, IgG3, and IgG4. This test typically evaluates the concentration of one or more of these subclasses. Each subclass has a distinct role in immunity, such as helping fight bacterial infections (IgG2) or enhancing immune responses (IgG1).

Why Might This Test Be Ordered?

Your healthcare provider may order this test to assess immune function, diagnose or monitor conditions like immunodeficiency, autoimmune diseases, or infections. For example, low levels of certain IgG subclasses might indicate a weakened immune response, while abnormal levels could suggest conditions like chronic infections or certain cancers.

How Is the Sample Collected?

A blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate the serum or plasma, which is sent to the lab for testing.

What Are Common Conditions Monitored With This Test?

This test is often used to monitor conditions such as common variable immunodeficiency (CVID), HIV/AIDS, certain autoimmune diseases, or to evaluate immune responses after vaccination. It can also help diagnose or manage infections that affect antibody production.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Testing

Frequently asked questions

How long does it take to get results from this test?
Results from this test are typically available within 1 to 3 business days, depending on the lab’s processing time. Your healthcare provider will discuss the results with you during your follow-up visit.
What does it mean if my IgG subclass levels are low?
Low levels of IgG subclasses may indicate an immune deficiency, where your body struggles to produce enough antibodies to fight infections. This could be due to genetic disorders, certain medications, or chronic illnesses. Your doctor may recommend additional tests or treatments to address the underlying cause.
Can diet or supplements affect IgG subclass levels?
While diet and supplements can influence overall immune function, they do not directly affect IgG subclass levels. However, maintaining a balanced diet rich in vitamins and minerals can support your immune system’s overall health. Always follow your healthcare provider’s advice regarding any dietary changes or supplements.
  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