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Serum Immunoglobulin G (IgG) by Immunoassay

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
24430-1
Short code
S suis Sertyp Islt Aggl
Synonyms
S suis Sertyp Islt Aggl
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
aggl
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?

IgG is the most common type of antibody in your blood. It plays a key role in defending your body against bacteria and viruses. This test helps doctors assess your immune system’s ability to fight infections and respond to vaccines.

Why Might You Need This Test?

Your doctor may order this test if you have symptoms of a weakened immune system, such as frequent infections, slow healing wounds, or if you’re being treated for conditions like autoimmune diseases, certain cancers, or after receiving certain medications that affect immunity.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The blood is then sent to a lab where it is analyzed using an immunoassay method to measure IgG levels.

What Are Common Results?

Results are typically reported as a concentration of IgG in the blood. While specific reference ranges can vary by lab, lower or higher than expected levels may indicate certain health conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What Causes Low IgG Levels?
Low IgG levels can be due to primary immunodeficiency disorders, certain medications that suppress the immune system, chronic liver disease, or conditions that affect protein production in the body.
What Causes High IgG Levels?
High IgG levels may be seen in chronic infections, autoimmune diseases, or certain cancers. They can also occur in response to repeated infections or as part of certain medical conditions.
How Often Should I Get This Test?
The frequency of this test depends on your medical condition and treatment plan. Your doctor will determine if and when you need retesting, often based on symptoms or as part of ongoing monitoring.
  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