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Serum or Plasma Immunoassay for Immunoglobulin G (IgG) Subclass 1 (IgG1) Concentration

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

This test measures the amount of a specific type of antibody (IgG1) in your blood. IgG antibodies are part of your immune system and help protect your body from infections.

Quick summary

["IgG1 helps fight bacteria and viruses, and its levels can vary based on immune response and health status."]

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

Key facts at a glance

LOINC
31309-8
Short code
C immitis Ab Fld Ql
Synonyms
C immitis Ab Fld Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 one of four main subclasses of Immunoglobulin G (IgG) antibodies. These antibodies are crucial for long-term immunity. The test detects the concentration of IgG1 in your blood, which can be influenced by immune responses, chronic infections, or certain medical conditions.

Why Might You Need This Test?

Your healthcare provider may order this test to evaluate immune function, diagnose or monitor conditions like autoimmune diseases, infections, or certain immune deficiencies. It can also help assess how well your immune system is responding to treatments.

Common Reasons for Testing

Common reasons include diagnosing or managing conditions such as chronic infections, autoimmune diseases (like rheumatoid arthritis or lupus), or assessing immune responses after vaccination or treatment for immune-related disorders.

Sample Collection and Preparation

A blood sample is typically collected from a vein in your arm. The blood is processed to separate serum or plasma, which is then analyzed using an immunoassay method to measure IgG1 levels accurately.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG1 Level

Frequently asked questions

How Might My Results Affect My Health?
Abnormally low IgG1 levels may indicate an immune deficiency or chronic immune suppression, while elevated levels could suggest an active immune response, such as in infections or certain autoimmune conditions. Your healthcare provider will interpret results in the context of your overall health and medical history.
What Does a Low IgG1 Level Mean?
A low IgG1 level might suggest an impaired immune response, which could be due to conditions like primary immunodeficiency, chronic illnesses, or certain medications that suppress the immune system. Further evaluation by your doctor may include additional tests to determine the cause.
What Does an Elevated IgG1 Level Mean?
Elevated IgG1 levels may be associated with chronic infections, autoimmune diseases, or an overactive immune response. Your doctor will discuss these findings with you and may recommend further testing or adjustments to your treatment plan.
  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