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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 by identifying and neutralizing harmful substances in your body."]

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

Key facts at a glance

LOINC
43368-0
Short code
MSI Tiss
Synonyms
MSI Tiss
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
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 Your Body?

IgG is the most abundant antibody in your blood and plays a critical role in defending against bacteria and viruses. It helps your immune system remember past infections, providing protection against future exposures. IgG is also involved in immune responses during pregnancy and fetal development.

Why Might Your Doctor Order This Test?

Your doctor may recommend this test to assess your immune system function. Possible reasons include evaluating immune deficiencies, diagnosing autoimmune diseases, checking for infections, or monitoring conditions like HIV, lupus, or certain cancers that affect antibody levels.

Common Reasons for Testing

Common reasons include diagnosing or monitoring immune-related conditions, assessing immune response after vaccination, or evaluating symptoms like frequent infections, fatigue, or unexplained illnesses.

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.

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 the results of this test?
Results are typically available within 1 to 3 business days, depending on your lab’s processing schedule. Your doctor will discuss the results with you during your follow-up visit.
What are the normal ranges for IgG levels?
Normal IgG levels vary by age and individual health. Your doctor will compare your results to your specific reference range and interpret them in the context of your overall health.
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. Your doctor may recommend lifestyle adjustments if they suspect underlying health concerns affecting your immune system.
  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