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Immunoassay for Immunoglobulin G (IgG) in Serum or Plasma

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."]

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

Key facts at a glance

LOINC
56524-2
Short code
IGF-I 45M p chal SerPl-mCnc
Synonyms
IGF-I 45M 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 Is Immunoglobulin G (IgG)?

IgG is the most common type of antibody in your blood. It plays a key role in defending your body against bacteria and viruses. Antibodies like IgG help your immune system recognize and remember invaders, such as germs, so your body can fight them off more quickly in the future.

Why Might You Need This Test?

Your doctor may order an IgG test if you have symptoms of low immunity, such as frequent infections, slow healing wounds, or unexplained fatigue. It can also be used to monitor conditions like certain autoimmune diseases, immune deficiencies, or to check for exposure to certain infections.

When Is This Test Done?

This test is typically done by drawing blood from a vein in your arm. The blood sample is sent to a lab where it is analyzed using an immunoassay method to measure IgG levels.

What Do IgG Levels Tell Your Doctor?

IgG levels can provide important clues about your immune system’s health. Low IgG levels might suggest an immune deficiency or problems with how your body produces antibodies. High levels could be seen in certain infections, chronic diseases, or as a side effect of certain treatments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG levels are important for diagnosing and managing conditions related to immune function, such as HIV, certain autoimmune diseases, or immune system disorders. They can also help determine if you have enough antibodies to protect against infections.

Short name

IgG Level

Frequently asked questions

What does a low IgG level mean?
A low IgG level may indicate an immune deficiency, where your body doesn’t produce enough antibodies to fight infections effectively. This can lead to frequent or severe illnesses. Your doctor may recommend further testing or treatments to address the underlying cause.
What does a high IgG level mean?
High IgG levels can be due to chronic infections, certain autoimmune diseases, or as a result of treatments like chemotherapy. It’s important to discuss these findings with your doctor to understand the possible causes and next steps.
How often should I get this test?
The frequency of this test depends on your medical condition and why it was ordered. Your doctor will determine the best timing based on your individual needs, such as monitoring treatment progress or managing an ongoing health issue.
  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