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Immunoglobulin G (IgG) in serum

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

This test measures the amount of Immunoglobulin G (IgG) in your blood. IgG is the most common type of antibody in your body and helps protect against 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
70256-3
Short code
Nuclear IgG Ser IA-Rto
Synonyms
Nuclear IgG Ser IA-Rto
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 Is Immunoglobulin G (IgG)?

IgG, or Immunoglobulin G, is the primary antibody found in your blood. It plays a crucial role in defending your body against bacteria and viruses. IgG antibodies are produced in response to infections and help neutralize toxins and pathogens. This test helps doctors assess your immune system’s ability to produce these protective proteins.

Why Might You Need This Test?

Your doctor may order an IgG test if you have symptoms of a weakened immune system, such as frequent infections, slow wound healing, or unexplained fatigue. It can also be used to monitor conditions like HIV, certain autoimmune diseases, or to check for immune deficiencies in newborns or infants.

When Is This Test Performed?

This test is typically done by drawing blood from a vein in your arm. The blood sample is sent to a lab for analysis. Results can help determine if your immune system is functioning properly or if there is an underlying issue requiring further medical evaluation.

What Are Possible Results?

Results for IgG levels are not always given in absolute numbers, as reference ranges can vary by lab and individual health. Your doctor will interpret the results in relation to your overall health and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What does a low IgG level mean?
A low IgG level may indicate an immune deficiency, where your body struggles to produce enough antibodies to fight infections. This can be due to genetic conditions, certain medications, or chronic illnesses. Your doctor may recommend additional tests or treatments to address the underlying cause.
What does a high IgG level mean?
High IgG levels can sometimes be a sign of an overactive immune response, such as in chronic infections, autoimmune diseases, or certain types of cancer. It may also be found in people with long-term inflammation or exposure to toxins. Your doctor will discuss these findings with you to determine the next steps.
How often should I get this test?
The frequency of IgG testing depends on your health condition. If you have an immune-related disorder, your doctor may recommend regular monitoring. Otherwise, this test is usually only done when symptoms or concerns suggest it is needed.
  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