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Immunoglobulin G (IgG) Subclass 1, Serum

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

This test measures the amount of Immunoglobulin G (IgG) subclass 1 in your blood. IgG is a type of antibody that helps protect your body from infections.

Quick summary

["IgG1 antibodies play a key role in fighting bacterial and viral infections."]

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

Key facts at a glance

LOINC
77679-9
Short code
IGF-I 3h p chal SerPl-mCnc
Synonyms
IGF-I 3h p chal SerPl-mCnc
Category
hormone
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 five subclasses of Immunoglobulin G (IgG), a major type of antibody in your blood. These subclasses have slightly different roles in your immune response. IgG1 is particularly important for defending against bacteria and viruses, helping your body recognize and remember pathogens for faster responses in the future.

Why Might Your Doctor Order This Test?

Your doctor 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.

How Is the Test Performed?

A blood sample is drawn from a vein in your arm. The blood is then sent to a lab where it is processed to separate the serum (liquid part of blood without clotting factors). The IgG1 level is measured using a specialized immunoassay technique.

What Are Common Reasons for Testing?

Common reasons include diagnosing or monitoring conditions like chronic infections, certain autoimmune diseases (such as rheumatoid arthritis or lupus), immune deficiencies, or evaluating immune responses to vaccines.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG1 Subclass (Serum)

Frequently asked questions

What Are Normal Results?
Normal results vary by lab and may not include a specific numeric range. Your results will be compared to your individual baseline and clinical context. Abnormal results may indicate immune system issues that need further evaluation.
How Do IgG1 Levels Change with Age?
IgG1 levels can vary with age. Infants have lower IgG1 levels compared to adults, and some conditions or treatments may temporarily alter these levels. Your doctor will consider your overall health and medical history when interpreting results.
Can Diet or Lifestyle Affect IgG1 Levels?
Diet and lifestyle factors like nutrition, stress, and overall health can influence immune function, potentially impacting antibody levels. However, IgG1 levels are primarily influenced by immune system activity and medical conditions rather than diet alone.
  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