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Immunoglobulin G (IgG) in serum/plasma by nephelometry

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

This test measures the amount of Immunoglobulin G (IgG), the most common type of antibody in your blood. IgG helps protect your body from infections and plays a key role in long-term immunity.

Quick summary

["IgG helps fight infections and supports immune function; levels can indicate immune response or deficiencies."]

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

Key facts at a glance

LOINC
100408-4
Short code
Emmental cheese IgG Qn
Synonyms
Emmental cheese IgG Qn
Category
chemistry
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 Is Immunoglobulin G (IgG)?

IgG is the primary antibody produced by your immune system to defend against bacteria, viruses, and toxins. It circulates in your blood and provides long-term immunity after an infection has passed. IgG is also important for protecting unborn babies through the placenta.

Why Might You Need This Test?

Your doctor may order an IgG test to evaluate your immune system, diagnose conditions like immunodeficiency, assess response to vaccines, or check for autoimmune diseases. It can also help monitor certain infections or diseases that affect antibody production.

When Could Your Results Be Abnormal?

Low IgG levels may suggest an immune deficiency, chronic infections, or conditions like celiac disease or inflammatory bowel disease. High IgG levels could indicate chronic infections, autoimmune disorders, or certain cancers.

What Does This Test Involve?

A blood sample is drawn from a vein in your arm. The sample is sent to a lab where it is analyzed using nephelometry, a method that measures the amount of IgG in your serum or plasma.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

Why do some people have lower than expected IgG levels?
Low IgG levels can occur due to genetic immune deficiencies, chronic illnesses (like HIV or cancer), or conditions that affect the gut (such as celiac disease or short bowel syndrome). Your doctor may recommend additional tests or treatments to address the underlying cause.
How do IgG levels change after vaccination?
IgG levels rise after vaccination to provide long-term immunity. If your IgG levels are low after vaccination, your doctor may recommend booster shots or immune support therapies.
Can IgG levels be affected by medications?
Yes, certain medications—like steroids, chemotherapy drugs, or some autoimmune medications—can lower IgG levels. If you’re taking medications, discuss potential effects with your doctor.
  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