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

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.

Quick summary

["IgG subclasses help identify specific immune responses and potential deficiencies."]

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

Key facts at a glance

LOINC
105981-5
Short code
IgG lamba Ser Ql IFE
Synonyms
IgG lamba Ser Ql IFE
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immunofixation
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 system disorders. It can also be part of a broader evaluation for certain genetic or chronic diseases.

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, similar to other routine blood tests. If you’re on blood thinners, let your provider know before the test.

What the Test Results Mean

IgG subclasses are measured in grams per liter (g/L) or milligrams per deciliter (mg/dL). Abnormal levels may indicate immune system issues, such as low production of certain antibodies or overactivity of the immune system.

Common Conditions Monitored

This test helps diagnose or monitor conditions like chronic infections, autoimmune diseases (e.g., lupus, rheumatoid arthritis), or immune deficiencies (e.g., common variable immunodeficiency). It may also be used to assess response to treatments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG Subclass Levels

Frequently asked questions

What does it mean if my IgG subclass levels are low?
Low IgG subclass levels may suggest an immune deficiency, which can make you more prone to infections. Your provider may recommend further testing or treatments to support your immune system.
What if my IgG subclass levels are high?
High IgG subclass levels might be seen in autoimmune diseases or chronic infections. This can help guide treatment decisions, such as adjusting medications or managing symptoms.
How often should I get this test?
The frequency depends on your health condition and treatment plan. Your healthcare provider will determine how often you need this test based on your individual needs and medical history.
  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