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Total Immunoglobulin G (IgG) in Serum

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

This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood. IgG helps protect your body from infections and is important for long-term immunity.

Quick summary

["IgG helps fight infections and supports long-term immunity by identifying and neutralizing harmful substances."]

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

Key facts at a glance

LOINC
24234-7
Short code
M pneumo IgG sp1 Ser-aCnc
Synonyms
M pneumo IgG sp1 Ser-aCnc
Category
chemistry
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 Is Immunoglobulin G (IgG)?

IgG is the most common type of antibody in your blood. Antibodies are proteins that help your immune system recognize and fight off bacteria, viruses, and other invaders. IgG is particularly important because it can cross the placenta to protect a developing fetus and provides long-lasting immunity after an infection has cleared.

Why Might You Need This Test?

Doctors may order an IgG test to check for low or high levels, which can indicate conditions like weakened immunity, certain infections, autoimmune diseases, or immune system disorders. It may also be used in monitoring treatments for conditions affecting the immune system.

When Is an IgG Test Performed?

This test is often done as part of a general health check, to diagnose or monitor conditions such as HIV/AIDS, chronic infections, or immune deficiencies. It can also be used to evaluate immune responses after vaccination or to assess how well a treatment is working for conditions like lupus or rheumatoid arthritis.

What Does the Test Involve?

A blood sample is taken from a vein, usually in your arm. The blood is then sent to a lab where it is analyzed to measure the IgG antibody levels. The test typically takes a few minutes to collect the sample and a few days to receive results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance of IgG Levels

Short name

IgG Level

Frequently asked questions

What Are Normal IgG Levels?
Normal IgG levels vary slightly between labs and individuals, but low levels may suggest immune system problems, such as severe combined immunodeficiency (SCID) or HIV/AIDS. High levels can sometimes indicate chronic infections, autoimmune diseases, or certain types of cancer.
How Do IgG Levels Change Over Time?
IgG levels can change with age, health status, and medical treatments. For example, newborns have lower IgG levels than adults because they receive antibodies from their mother during pregnancy. Chronic illnesses or treatments like chemotherapy can also affect IgG levels.
Can IgG Levels Be Affected by Medications?
Yes, certain medications—such as steroids, chemotherapy drugs, or immune-suppressing treatments—can lower IgG levels. Always discuss any medications you’re taking with your healthcare provider, as they may impact your test results.
  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