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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
86135-1
Short code
S pneum Da 5 IgG 2:1 Ser-Rto
Synonyms
S pneum Da 5 IgG 2:1 Ser-Rto
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 helps fight infections by marking harmful substances for destruction and activating immune responses. Levels can vary depending on your health, immune system activity, and exposure to infections.

Why Might You Need This Test?

Your doctor may order this test to check for immune system function, diagnose or monitor conditions like immunodeficiency, autoimmune diseases, or infections. It can also help evaluate responses to vaccines or treatments.

When Might You Get This Test?

You might have this test if you have symptoms like frequent infections, fatigue, or if your doctor suspects an immune disorder. It’s also sometimes included in routine blood work or during pregnancy.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a fasting blood panel. Bring any medications or questions to your doctor’s office.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

How low or high might my IgG levels be?
IgG levels can be low in people with weakened immune systems (e.g., due to HIV/AIDS, chemotherapy, or genetic disorders like Common Variable Immunodeficiency). High levels may suggest chronic infections, inflammation, or certain autoimmune conditions.
Will my IgG levels change over time?
Yes, IgG levels can fluctuate due to infections, vaccinations, aging, or medical treatments. Regular monitoring helps track immune health, especially in people with chronic conditions.
What does it mean if my IgG test is abnormal?
An abnormal IgG result may prompt further testing to explore underlying causes, such as immune deficiencies, chronic illnesses, or reactions to treatments. Your doctor will discuss next steps based on your symptoms and test results.
  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