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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) in your blood. IgG is a type of antibody that helps your immune system fight infections and diseases.

Quick summary

["IgG helps protect your body from infections and supports long-term immunity."]

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

Key facts at a glance

LOINC
98956-6
Short code
C immitis IgM Spec IA-aCnc
Synonyms
C immitis IgM Spec IA-aCnc
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 defending against bacteria and viruses. Your body produces IgG in response to infections or vaccines to help you stay healthy over time.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system problems, such as low levels that could indicate conditions like HIV, certain cancers, or severe infections. It can also help monitor immune responses after treatments like chemotherapy or organ transplants.

Sample Collection and Preparation

A blood sample is taken from a vein, usually in your arm. The blood is then sent to a lab for testing. The test measures the concentration of IgG in your serum, the liquid part of blood without blood cells.

What Are Common Reasons for Testing?

Tests for IgG are often done when symptoms like frequent infections, unexplained fatigue, or signs of immune disorders appear. It may also be part of routine checks for people with weakened immune systems or those receiving immune-suppressing treatments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG levels can be lower in people with immune deficiencies, chronic illnesses, or certain autoimmune diseases. High levels might suggest overactive immune responses or certain infections. Always discuss results with your healthcare provider for proper interpretation.

Short name

IgG Level

Frequently asked questions

How Long Does It Take to Get Results?
Results are typically available within 1 to 3 business days, depending on lab processing times. Your doctor will discuss the results with you during your follow-up visit.
What Does a Low IgG Level Mean?
Low IgG levels can mean your immune system isn’t producing enough antibodies to fight infections effectively. This might happen with conditions like HIV, certain cancers, or long-term illnesses that weaken the immune system.
What If My IgG Level Is Abnormally High?
High IgG levels may indicate an overactive immune response, chronic infections, or certain autoimmune diseases. Your doctor will review your symptoms and medical history to explain further.
  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