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Immunoglobulin G (IgG) mass concentration 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 diseases.

Quick summary

["IgG levels can indicate immune function and response to infections or treatments."]

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

Key facts at a glance

LOINC
2466-1
Short code
IgG1 Ser-mCnc
Synonyms
IgG1 Ser-mCnc
Category
chemistry
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. Antibodies are proteins that help your immune system fight infections and diseases. IgG is particularly important because it can cross the placenta to protect a baby during pregnancy and provide long-term immunity after vaccination or infection.

Why might you need this test?

Doctors may order this test to evaluate your immune system, diagnose or monitor conditions like immunodeficiency, check response to vaccines, or assess immune responses to infections. It can also be used in research or specialized clinical settings to study antibody levels.

How is the test performed?

A blood sample is taken from a vein, usually in your arm. The blood is then processed to separate the serum (the liquid part without clots) for testing. The IgG level is measured using a specialized laboratory technique to determine its mass concentration.

What does a low or high IgG level mean?

Low IgG levels may suggest a weakened immune system, conditions like common variable immunodeficiency, or certain chronic illnesses. High IgG levels can sometimes indicate chronic infections, autoimmune diseases, or overactive immune responses.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

Why do I need this test?
Your healthcare provider may recommend this test to check how well your immune system is working, to diagnose or manage conditions affecting antibodies, or to monitor treatment responses.
What does the test involve?
You’ll have a small needle inserted into your arm to draw blood. The blood is then sent to a lab where it is analyzed to measure IgG levels. This process usually takes a few minutes and is generally safe with minimal discomfort.
Can I eat or drink before this test?
You can typically eat and drink normally before the test unless your doctor specifies otherwise. However, follow any specific instructions they provide to ensure accurate results.
  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