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Immunoglobulin G (IgG)

Published: July 27, 2026Updated: August 25, 2026

IgG is the most abundant type of antibody in the blood and is crucial for fighting bacterial and viral infections. It is also involved in the secondary immune response.

Quick summary

IgG is a key antibody in the blood that helps fight infections and is measured to assess immune function.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
mg/dL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Roche IgG, Abbott IgG, Siemens IgG, Beckman IgG
interpretation: {"text":"May indicate immunodeficiency, malnutrition, or certain types of leukemia. Further testing is required for a definitive diagnosis.","label":"Low IgG"}; {"text":"May suggest chronic inflammation, autoimmune disorders, or chronic infections. Additional tests are needed to confirm the cause.","label":"High IgG"}

Immunoglobulin G (IgG) is the most common type of antibody found in the blood and other body fluids. It plays a critical role in providing protection against bacterial and viral infections by neutralizing pathogens and facilitating their destruction by the immune system.

IgG levels are often measured to evaluate the overall health of the immune system and to diagnose conditions such as immunodeficiency, autoimmune disorders, and chronic infections. High or low levels of IgG can indicate various underlying health issues.

Normal IgG levels in adults typically range from 700 to 1600 mg/dL. Levels below this range may suggest an immunodeficiency, while higher levels could indicate chronic inflammation or an overactive immune response.

Frequently asked questions

What causes low IgG levels?
Low IgG levels can be caused by conditions such as immunodeficiency disorders, malnutrition, and certain types of cancer, including leukemia.
What does a high IgG level mean?
High IgG levels may indicate chronic inflammation, autoimmune disorders, or chronic infections. Further diagnostic tests are needed to determine the exact cause.
  1. 1
    Immunoglobulin G (IgG) TestSource
  2. 2
    IgG: The Major AntibodySource

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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 25, 2026. · Read our editorial policy