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Immunoglobulin G (IgG) in Serum or Plasma by Mass Concentration

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 the most common antibody and plays a key role in fighting infections and diseases.

Quick summary

["IgG helps your immune system defend against bacteria and viruses."]

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

Key facts at a glance

LOINC
56122-5
Short code
IgG BldCo-mCnc
Synonyms
IgG BldCo-mCnc
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What Does IgG Measure?

IgG is the primary antibody your body produces to protect against infections. It’s found in all body fluids but is most concentrated in the blood. Levels can vary based on your immune response, health status, and certain medical conditions.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system function, diagnose conditions like immunodeficiency, monitor treatment for diseases like lupus or HIV, or evaluate immune responses in newborns or chronic illnesses.

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 where it is analyzed using a specialized technique to measure IgG concentration accurately.

What to Expect Before the Test

There are usually no special preparations needed. You may have some mild discomfort from the needle, but this usually fades quickly. If you’re on blood thinners or have a history of bleeding issues, let your doctor know.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What causes IgG levels to be low?
Low IgG levels can result from conditions like primary immunodeficiency, chronic illnesses (e.g., HIV/AIDS), malnutrition, or certain medications that affect the immune system. It may also appear in newborns due to maternal antibodies waning.
What causes IgG levels to be high?
High IgG levels can be seen in chronic infections, autoimmune diseases (like lupus or rheumatoid arthritis), certain cancers, or as a reaction to vaccines. In some cases, it may also be due to overproduction of antibodies by the immune system.
Can IgG levels change over time?
Yes, IgG levels can fluctuate based on health status, infections, vaccinations, or treatments. For example, after an infection, your body may produce more IgG to fight it off. Regular monitoring may be needed if you have a chronic condition affecting your immune system.
  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