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Immunoassay for Total Immunoglobulin G (IgG) in Serum/Plasma

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

This test measures the amount of Immunoglobulin G (IgG), a key protein in your immune system that helps fight infections. IgG is the most common type of antibody in your blood.

Quick summary

["IgG helps protect your body against bacteria and viruses, and plays a role in long-term immunity."]

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

Key facts at a glance

LOINC
31021-9
Short code
INF-B1 NAb Titr SerPl Nt
Synonyms
INF-B1 NAb Titr SerPl Nt
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
neut
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 antibodies are produced by your immune system in response to infections and vaccines. They provide long-lasting protection by staying in your bloodstream longer than other antibodies. IgG also crosses the placenta to protect newborns from infections during pregnancy and early life.

Why Might Your Doctor Order This Test?

Your doctor may check IgG levels if you have symptoms of a weakened immune system, such as frequent infections, slow wound healing, or unexplained fatigue. It can also be used to monitor immune responses after vaccines or treatments like chemotherapy.

Common Reasons for Testing

Tests for IgG are often done to diagnose or monitor conditions like immunodeficiency disorders, autoimmune diseases, or to check immune function before or after certain treatments.

Sample Collection and Preparation

A blood sample is taken from a vein, usually in your arm. The blood is then processed to separate the serum or plasma for testing. This test does not require fasting.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG levels can be influenced by various factors, including age, overall health, recent infections, and certain medications. High or low IgG levels may indicate underlying health issues that need further evaluation by a healthcare provider.

Short name

IgG Level

Frequently asked questions

What Are Normal IgG Levels?
There are no specific numeric reference ranges provided here since they can vary by lab and patient demographics. Your doctor will interpret the results in the context of your overall health and medical history.
How Long Does It Take to Get Results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing schedule. Follow-up with your healthcare provider to discuss the results and any next steps.
Can IgG Levels Change Over Time?
Yes, IgG levels can fluctuate due to infections, vaccinations, immune responses, or certain medical conditions. Regular monitoring may be recommended if you have a chronic condition 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