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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 play a key role in long-term immunity."]

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

Key facts at a glance

LOINC
109303-8
Short code
HTLV I+II IgG Msmt Ser
Synonyms
HTLV I+II IgG 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 common type of antibody in your blood. It helps fight off infections by marking harmful substances for destruction and boosting immune responses. Levels can vary based on your health, immune status, and exposure to pathogens.

Why Might You Need This Test?

Your doctor may order an IgG test to check for immune system function, diagnose conditions like immunodeficiency, evaluate immune responses to vaccines, or monitor chronic diseases such as lupus or rheumatoid arthritis.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The blood is then sent to a lab for analysis. The test measures the concentration of IgG antibodies in your serum.

What Are Common Results?

Results are typically reported as a concentration in grams per liter (g/L). While reference ranges can vary by lab, lower than expected levels may suggest weakened immunity, while higher levels could indicate chronic infections, autoimmune conditions, or other health issues.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low IgG levels may indicate primary immunodeficiency, chronic infections, or malabsorption issues. High IgG levels can be seen in autoimmune diseases, chronic infections, or certain cancers. Monitoring IgG levels helps guide treatment plans and manage immune-related conditions effectively.

Short name

IgG Level

Frequently asked questions

What Causes Low IgG Levels?
Conditions like severe immune deficiencies, certain cancers, or long-term malnutrition can lead to lower IgG levels. Some medications or treatments may also affect antibody production.
What Causes High IgG Levels?
Chronic infections, autoimmune diseases (such as lupus or rheumatoid arthritis), or certain cancers may cause elevated IgG levels. Long-term exposure to allergens or certain medications can also play a role.
How Often Should I Get This Test?
Your doctor will determine how often you need this test based on your medical history, symptoms, and treatment plan. Regular monitoring may be necessary if you have an ongoing health 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