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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."]

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

Key facts at a glance

LOINC
110137-7
Short code
S pneum Da 1 IgG Msmt Ser
Synonyms
S pneum Da 1 IgG Msmt Ser
Category
coagulation
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 plays a key role in defending against bacteria and viruses, including those that cause pneumonia, meningitis, and other infections. IgG also helps your body remember past infections, which is why it’s important for long-term immunity.

Why Might You Need This Test?

Your doctor may order an IgG test to check for immune system function, diagnose conditions like immunodeficiency, evaluate responses to vaccines, or assess how well your body is producing antibodies in response to infections or treatments.

Common Reasons for Testing

Common reasons include diagnosing conditions like HIV, lupus, or other autoimmune diseases, checking for low antibody levels in newborns or people with weakened immune systems, or monitoring immune responses after vaccination.

Sample Collection and Preparation

This test uses a blood sample drawn from a vein in your arm. After drawing blood, it is sent to a lab for analysis. The lab will separate the serum (the liquid part of blood without clots) for testing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

How is IgG Level Important in Health?
Low IgG levels may indicate an immune deficiency, where your body struggles to fight infections effectively. High IgG levels might suggest an overactive immune response, chronic infections, or certain autoimmune conditions. Monitoring IgG helps doctors manage conditions like HIV, lupus, or chronic infections.
What Does a Low IgG Level Mean?
A low IgG level could mean your immune system isn’t working as well as it should, increasing your risk of frequent or severe infections. This might happen in people with certain genetic disorders, HIV, or after treatments that weaken the immune system.
Can IgG Levels Change Over Time?
Yes, IgG levels can change due to infections, vaccinations, aging, or certain medical conditions. For example, vaccinations can temporarily boost IgG levels, while chronic illnesses or immune disorders may lead to long-term changes.
  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