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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 is important for long-term immunity.

Quick summary

["IgG helps fight infections and supports long-term immunity by marking harmful substances for destruction."]

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

Key facts at a glance

LOINC
111027-9
Short code
L pneumo IgG Msmt Ser
Synonyms
L pneumo 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 Is Immunoglobulin G (IgG)?

IgG is the most common type of antibody in your blood. It plays a key role in defending your body against bacteria and viruses. After an infection, IgG helps your immune system remember it to fight off future attacks more quickly. Levels of IgG can vary depending on your health, immune response, and overall immune system function.

Why Might You Need This Test?

Your doctor may order an IgG test to check for immune system issues, such as low or high levels that could indicate conditions like immunodeficiency, autoimmune diseases, or infections. It may also be used to monitor treatment progress for conditions affecting immunity.

When Might You Get Results Back?

Results are typically available within 1 to 3 business days, depending on your lab’s processing time. Your doctor will discuss the results and any next steps with you.

What Could High or Low IgG Levels Mean?

High IgG levels might suggest chronic infections, certain immune disorders, or overactive immune responses. Low IgG levels could indicate weakened immunity, conditions like HIV/AIDS, or certain genetic disorders that impair antibody production.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG Level

Frequently asked questions

How long does it take for IgG levels to change after an infection or vaccination?
IgG levels can take several weeks to months to fully develop after an infection or vaccination. Some people may see a temporary rise or drop depending on their immune response, but results can vary widely.
Can diet affect IgG levels?
Diet can influence overall immune function, but it does not directly affect IgG levels. A balanced diet supports immune health, but IgG is primarily produced by your immune system in response to infections or vaccines.
Is IgG testing the same as checking for antibodies to a specific illness?
No, IgG testing measures total antibody levels, while specific antibody tests (like those for COVID-19 or other infections) identify antibodies to particular pathogens. IgG alone does not indicate a specific illness.
  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