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Serum Immunoglobulin G (IgG) Level

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 binding to pathogens."]

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

Key facts at a glance

LOINC
21424-7
Short code
Nuclear IgG Ser Ql IF
Synonyms
Nuclear IgG Ser Ql IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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 Does IgG Serve in the Body?

IgG is the most abundant antibody in your blood and plays a critical role in defending against bacteria and viruses. It can cross the placenta to provide passive immunity to newborns and helps clear toxins and immune complexes from your system.

Why Might You Need This Test?

Doctors may order an IgG test to evaluate immune function, diagnose conditions like immunodeficiency, monitor treatment responses for autoimmune diseases, or check for infections in people with weakened immune systems.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is processed to separate serum (the liquid part without clotting factors) for testing. This test does not require fasting.

Common Reasons for Testing

Common reasons include assessing immune system health, diagnosing conditions like HIV, chronic infections, or autoimmune diseases, and monitoring immune responses during treatment.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

Low IgG levels may indicate an immune deficiency, chronic infections, or malabsorption issues, while very high levels could suggest autoimmune disorders or certain cancers. IgG levels alone are not diagnostic but are often part of a broader evaluation.
IgG levels can vary based on age, overall health, and medical conditions. If your IgG level is outside typical ranges, your doctor may recommend further testing or additional questions about your health history.
What does a low IgG level mean?
A low IgG level may suggest a weakened immune system, which could increase your risk of infections. Your doctor may investigate underlying causes such as genetic disorders, chronic illnesses, or malabsorption problems.
What causes high IgG levels?
High IgG levels can be due to autoimmune diseases, chronic infections, certain cancers, or long-term exposure to toxins. Your doctor will consider your medical history and other test results to determine the cause.
  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