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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) in your blood. IgG is a type of antibody that helps protect your body from infections.

Quick summary

["IgG helps fight infections and supports long-term immunity."]

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

Key facts at a glance

LOINC
94449-6
Short code
HLA class I Ab.IgG high risk SerPl FC
Synonyms
HLA class I Ab.IgG high risk SerPl FC
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
flow-cytometry
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 plays a key role in defending your body against bacteria and viruses. Levels of IgG can vary depending on your immune response, overall health, and certain medical conditions.

Why Might You Need This Test?

Your healthcare provider may order this test to check for low or high IgG levels, which can indicate immune system issues, such as infections, autoimmune diseases, or conditions like HIV, where the immune system is weakened.

What Could Abnormal Results Mean?

Low IgG levels might suggest a weakened immune system, which can make you more prone to infections. High IgG levels could be due to chronic infections, certain autoimmune diseases, or other health conditions that stimulate the immune system.

How Is This Test Done?

A blood sample is taken from a vein in your arm. The sample is sent to a lab where it is analyzed to measure the IgG concentration.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG levels are important for diagnosing and monitoring conditions that affect the immune system. They help healthcare providers understand how well your body is protecting itself from infections and other diseases.

Short name

IgG Level

Frequently asked questions

What does a low IgG level mean?
A low IgG level may indicate an immune deficiency, where your body has trouble fighting off infections. This could be due to genetic conditions, certain medications, or conditions like HIV/AIDS that weaken the immune system.
What does a high IgG level mean?
High IgG levels can be linked to chronic infections, autoimmune diseases (like rheumatoid arthritis), or other conditions that cause prolonged immune system activity. Your doctor will review your medical history and other test results to determine the cause.
How often should I get this test?
The frequency of this test depends on your health condition and medical needs. Your healthcare provider will determine how often you need it based on your symptoms, medical history, and treatment plan.
  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