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Immunoglobulin G (IgG) by Serum Immunoassay

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of Immunoglobulin G (IgG), a type of antibody found in your blood. IgG helps protect your body from infections and is the most common type of antibody.

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
47323-1
Short code
Deprecated S pneum17 IgG Ser IA-mCnc
Synonyms
Deprecated S pneum17 IgG Ser IA-mCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 primary antibody in your blood that provides immunity against bacteria and viruses. It’s produced by your immune system in response to infections or vaccines. IgG antibodies remain in your bloodstream for a long time, helping you stay protected even after the initial infection has passed.

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’s also used in monitoring treatment responses for conditions like HIV, hepatitis, or cancer.

When Is an IgG Test Performed?

This test is often done when you have symptoms like frequent infections, unexplained fatigue, or if you’re being treated for a condition that affects your immune system. It may also be part of routine blood work for certain health checks or before receiving certain vaccines.

How Is the Test Done?

A small amount of blood is drawn from a vein in your arm. The blood sample is then sent to a lab for testing using an immunoassay method to measure IgG levels.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What does an IgG test tell your doctor?
Low IgG levels may suggest an immune system disorder, such as severe combined immunodeficiency (SCID) or other primary immunodeficiencies. High IgG levels can sometimes indicate chronic infections, autoimmune diseases, or certain types of cancer, though they’re more commonly found in response to infections.
How long does it take to get results?
Results from an IgG test are typically available within 1 to 3 business days, depending on your lab’s processing time. Your doctor will discuss the results with you during your follow-up visit.
Can diet or supplements affect IgG levels?
Dietary changes or supplements generally do not directly affect IgG levels, as IgG is produced by your immune system in response to infections or vaccines. However, maintaining a balanced diet supports overall immune function.
  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