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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 binding to pathogens."]

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

Key facts at a glance

LOINC
10403-4
Short code
Inject Serum Ig Vol Patient
Synonyms
Inject Serum Ig Vol Patient
Category
chemistry
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. Antibodies are proteins that help your immune system recognize and fight off harmful substances like bacteria and viruses. IgG is particularly important for providing long-term immunity after you recover from an infection.

Why Might You Need This Test?

Doctors may order an IgG test to check for low or high levels, which can indicate conditions like immune deficiencies, certain infections, or autoimmune diseases. It’s also used in monitoring treatments for conditions that affect the immune system.

Common Reasons for Testing

Common reasons include diagnosing or monitoring immune-related disorders, evaluating responses to vaccines, or assessing conditions like HIV, lupus, or chronic infections.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate the serum (the liquid part without clotting factors) for testing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

How long does it take to get results from this test?
Results are typically available within 1 to 3 business days, depending on your lab’s processing schedule. Your healthcare provider will discuss the results with you.
What do my IgG results mean?
Results may be compared to a reference range provided by your lab. Low IgG levels might suggest an immune deficiency, while very high levels could indicate chronic infections, certain cancers, or autoimmune diseases. Your doctor will interpret the results in the context of your health history and symptoms.
Can lifestyle changes affect IgG levels?
While diet and overall health can influence immune function, IgG levels are primarily determined by your body’s immune response. Stress, poor sleep, or chronic illnesses may indirectly affect immune health, but IgG testing itself does not change based on lifestyle alone.
  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