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Immunoassay for Immunoglobulin G (IgG) Subclass 1 (IgG1) in Serum

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

This test measures the level of Immunoglobulin G1 (IgG1), one of the main types of antibodies in your blood. IgG1 helps protect against infections and plays a role in immune responses.

Quick summary

["IgG1 levels can help assess immune function and identify potential immune system imbalances."]

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

Key facts at a glance

LOINC
42331-9
Short code
Nuclear IgG Ser FC-aCnc
Synonyms
Nuclear IgG Ser FC-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
flow-cytometry
CPT
86430
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?

IgG1 is a subtype of Immunoglobulin G (IgG), which is the most common antibody in your blood. This test specifically looks at the concentration of IgG1, which can vary depending on your health and immune status. IgG1 is involved in fighting bacterial and viral infections and is also linked to allergic reactions and autoimmune responses.

Why Might Your Doctor Order This Test?

Your doctor may recommend this test if they suspect an immune-related condition, such as an infection, allergy, or autoimmune disorder. It can also be used to monitor treatment responses in certain conditions like chronic infections or immune deficiencies.

Preparation for the Test

No special preparation is usually needed for this blood test. You may be asked to fast for a few hours before the test if instructed by your healthcare provider, but this is not always required for antibody tests like IgG1.

What to Expect During the Test

A healthcare professional will draw blood from a vein in your arm. This process is quick and typically painless. You may feel a slight pinch or discomfort, but most people tolerate it well. The blood sample will be sent to a lab for analysis.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG1 Subclass Test

Frequently asked questions

How Does This Test Differ from Other IgG Tests?
This test specifically measures IgG1, one of the four subclasses of IgG antibodies. Other IgG subclasses (IgG2, IgG3, IgG4) are also measured separately if needed. IgG1 is often the most abundant subclass and is particularly important for fighting bacterial infections.
What Are Common Conditions Monitored with IgG1 Testing?
IgG1 testing is often used in the evaluation of chronic infections (e.g., tuberculosis, HIV), immune deficiencies, autoimmune diseases (e.g., rheumatoid arthritis), and allergic responses. It can also help assess vaccine responses, especially in individuals with weakened immune systems.
Can IgG1 Levels Change Over Time?
Yes, IgG1 levels can fluctuate depending on your health, immune response to infections or vaccines, and certain medical treatments. For example, during an infection, IgG1 levels may rise as your body produces more antibodies to fight the illness. Chronic conditions or treatments like chemotherapy may also affect IgG1 levels.
  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