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Total 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 fight infections and is important for long-term immunity.

Quick summary

["IgG helps protect your body from infections and supports long-term immunity."]

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

Key facts at a glance

LOINC
25283-3
Short code
Deprecated S pneum23 IgG 2:1 Ser-Rto
Synonyms
Deprecated S pneum23 IgG 2:1 Ser-Rto
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 Is Immunoglobulin G (IgG)?

IgG is the most common type of antibody in your blood. It plays a key role in defending against bacteria and viruses, helping your immune system remember past infections for faster protection if you encounter the same germs again. Levels of IgG can vary depending on your health, immune status, and exposure to infections.

Why Might You Need This Test?

Your doctor may order an IgG test to check for low or high levels, which can indicate conditions like immune deficiencies, chronic infections, or certain autoimmune diseases. It may also be used to monitor treatment responses in people with weakened immune systems.

How Is This Test Done?

A small blood sample is taken from a vein in your arm. The blood is then sent to a lab where it is processed to measure IgG levels using an immunoassay method, which detects antibodies in your serum.

What Are Common Reasons for Testing?

Common reasons include diagnosing or monitoring immune-related conditions, assessing immune function in people with chronic illnesses, or evaluating responses to treatments like vaccines or medications that boost immunity.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What does a low IgG level mean?
Low IgG levels may suggest an immune deficiency, such as common variable immunodeficiency (CVID), or could be seen in people with chronic illnesses like HIV/AIDS, certain cancers, or long-term malnutrition. It can also occur in newborns or premature infants due to incomplete immune development.
What does a high IgG level mean?
High IgG levels can sometimes be normal, especially in people with repeated infections or chronic conditions. However, they may also indicate conditions like certain autoimmune diseases, chronic inflammation, or exposure to toxins. Rarely, high IgG can be associated with monoclonal gammopathies, where abnormal proteins build up in the blood.
How often should I get this test?
The frequency of IgG testing depends on your health condition and medical needs. Your doctor will determine how often you need this test based on your symptoms, diagnosis, or treatment plan.
  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