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Serum Immunoglobulin G (IgG) by Immunoassay

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.

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
85991-8
Short code
S pneum Da 14 IgG Ser-mCnc
Synonyms
S pneum Da 14 IgG Ser-mCnc
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 This Test Measure?

IgG is the most common type of antibody in your blood. It plays a key role in defending against bacteria and viruses. Your body produces IgG in response to infections and vaccines. Levels can vary depending on your immune response, overall health, and exposure to pathogens.

Why Might Your Doctor Order This Test?

Your doctor may check IgG levels if you have symptoms of low immunity, such as frequent infections, delayed healing, or if you’re being treated for conditions like HIV, lupus, or certain autoimmune diseases. It can also be part of monitoring for immune-related treatments or conditions like congenital immunodeficiency.

Common Reasons for Testing

IgG testing is often done to diagnose or monitor conditions affecting the immune system. It may also be used before certain vaccines to ensure adequate antibody response.

Sample Collection and Preparation

A blood sample is taken from a vein in your arm. The blood is processed to separate serum (the liquid part without clots) for testing. This test does not require fasting.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What Are Normal IgG Levels?
There is no single 'normal' range for IgG because it can vary widely among individuals. Your doctor will compare your result to your baseline or specific clinical context.
How Long Does It Take to Get Results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing schedule.
Can IgG Levels Change Over Time?
Yes, IgG levels can fluctuate due to infections, vaccinations, aging, or underlying health conditions. Regular monitoring may be needed if you have a chronic illness or immune-related treatment.
  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