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Serum Immunoglobulin G (IgG) Level

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 antibodies support long-term immunity and are often checked if you have concerns about immune function or recurrent infections."]

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

Key facts at a glance

LOINC
109379-8
Short code
GM3 IgM Msmt Ser
Synonyms
GM3 IgM Msmt Ser
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 Does IgG Measure?

IgG is the most abundant antibody in your blood, playing a key role in defending against bacteria and viruses. It circulates in your serum (liquid part of blood after clotting) and helps your immune system remember past infections for faster protection if you encounter the same pathogen again.

Why Might You Need This Test?

Doctors may order an IgG test if you have symptoms like frequent infections, weakened immune response, or if you’re being evaluated for conditions like HIV, autoimmune diseases, or certain cancers. It can also help monitor treatment progress in immune-related conditions.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate serum, which is sent to the lab for testing. No special preparation is needed, but fasting may be advised depending on your doctor’s instructions.

What to Expect After Testing

Results are typically available within a few days. Your doctor will interpret the results in relation to your health history and symptoms. If your IgG levels are low, additional tests may be needed to explore underlying causes.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG Level

Frequently asked questions

What Are Normal IgG Levels?
Normal IgG levels vary by age and health status, but low levels may suggest immune deficiencies or chronic illnesses. High levels could indicate chronic infections, certain autoimmune diseases, or overactive immune responses.
Can IgG Levels Change Over Time?
Yes, IgG levels can fluctuate due to infections, vaccinations, aging, or medical treatments. Regular monitoring may be recommended if you have a chronic condition affecting your immune system.
Does Diet Affect IgG Levels?
Dietary factors like protein intake or certain foods may indirectly support immune function, but IgG levels are primarily influenced by your immune response and overall health.
  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