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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 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
56634-9
Short code
Nuclear IgG Titr Ser IF
Synonyms
Nuclear IgG Titr Ser IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
8
Ref high
61
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
CPT
82977
SNOMED
3110003
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 Serve in Your Body?

IgG is the most abundant antibody in your blood and plays a critical role in defending against bacterial and viral infections. It also helps neutralize toxins and supports immune memory, which aids in preventing future infections.

Why Might You Need This Test?

Your healthcare provider may order an IgG test to check for immune system function, diagnose conditions like immunodeficiency, evaluate responses to vaccines, or assess issues related to antibody production in chronic diseases.

Common Reasons for Testing

Common reasons include diagnosing immune deficiencies, monitoring immune responses to treatments (e.g., chemotherapy), evaluating vaccine effectiveness, or investigating symptoms like frequent infections, fatigue, or autoimmune conditions.

Sample Collection and Preparation

A blood sample is drawn from a vein, typically in your arm. The blood is sent to a lab where it is processed to separate serum (the liquid part without clotting factors). The IgG level is then measured using an immunoassay method.

Reference range

Adult males: 8-61 U/L; Adult females: 5-36 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG Levels and Their Clinical Significance

Short name

IgG Level

Frequently asked questions

What Are Normal IgG Levels?
Normal IgG levels vary slightly among labs, but low levels may suggest an immune deficiency, while very high levels could indicate chronic infections, autoimmune diseases, or certain cancers. Your results will be compared to your lab’s reference range.
Can IgG Levels Change Over Time?
Yes, IgG levels can fluctuate due to infections, vaccinations, medications, or underlying health conditions. Repeated testing may be needed to track changes over time.
What Does It Mean If My IgG Level Is Abnormal?
Abnormal IgG levels can signal immune system issues. Low IgG might mean your body struggles to fight infections, while high levels could indicate chronic inflammation or immune activation. Always discuss results with your healthcare provider.
  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