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Serum IgG Immunoglobulin Level (Quantitative)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood. IgG is important for fighting infections and long-term immunity.

Quick summary

["IgG helps protect your body from diseases by identifying and neutralizing harmful substances."]

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

Key facts at a glance

LOINC
29950-3
Short code
Nuclear IgG Ser Ql IA
Synonyms
Nuclear IgG Ser Ql IA
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 providing immunity against infections, such as bacteria and viruses. Your body produces IgG in response to vaccines, infections, or chronic illnesses. This test helps doctors assess your immune system’s ability to fight off infections and monitor conditions like autoimmune diseases or immune deficiencies.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system function, diagnose conditions like HIV, lupus, or other autoimmune diseases, evaluate immune responses after vaccines, or monitor treatment progress for chronic illnesses.

How Is the Test Performed?

A blood sample is taken from a vein in your arm. The blood is then sent to a lab for analysis using an immunoassay method to measure IgG levels.

What Are Common Results?

Results are typically reported as a concentration (e.g., grams per liter). While reference ranges vary by lab, lower than expected IgG levels may suggest immune system issues, while higher levels could indicate chronic infections or certain diseases.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG Level

Frequently asked questions

What Does a Low IgG Level Mean?
Low IgG levels may indicate an immune deficiency, such as severe combined immunodeficiency (SCID) or other congenital or acquired immune disorders. It can also be seen in chronic liver disease or malnutrition.
What Does a High IgG Level Mean?
High IgG levels are often seen in chronic infections (e.g., hepatitis, HIV), autoimmune diseases (e.g., rheumatoid arthritis), or after repeated infections. Rarely, it may be due to certain medications or genetic conditions.
How Often Should I Get This Test?
The frequency depends on your health condition. Doctors may recommend periodic testing for people with immune-related diseases, those recovering from infections, or those on long-term immune-boosting treatments.
  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