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Immunoglobulin G (IgG) mass concentration in serum/plasma

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

This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood. IgG helps protect your body from infections and is the most common antibody in the blood.

Quick summary

["IgG antibodies play a key role in long-term immunity."]

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

Key facts at a glance

LOINC
33952-3
Short code
IC IgM SerPl-mCnc
Synonyms
IC IgM SerPl-mCnc
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 most abundant antibody in your blood. It’s produced by your immune system to fight off infections, including bacteria and viruses. Unlike other antibodies, IgG can cross the placenta to provide temporary immunity to a newborn. This test helps doctors assess your immune response and identify potential deficiencies or excesses.

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’s also used in diagnosing conditions like HIV, certain autoimmune diseases, or to monitor treatment responses in patients with immune-related disorders.

Common Reasons for Testing

Common reasons include evaluating immune function in newborns, diagnosing immune deficiencies, monitoring chronic illnesses, or checking for infections where IgG levels may be abnormal. It can also be part of a broader workup for unexplained symptoms related to immunity.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for a few hours before the blood draw if your doctor specifies it. On the day of the test, wear a loose shirt and avoid smoking or consuming caffeine for 30 minutes before your blood draw.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What does an abnormal IgG level mean?
Low IgG levels may indicate an immune deficiency, such as common variable immunodeficiency (CVID), which can make you more susceptible to infections. Very low levels in newborns could signal a congenital immune disorder. High IgG levels might suggest chronic infections, autoimmune diseases, or certain types of cancer, such as multiple myeloma.
How often should I get this test?
Your doctor will determine how often you need this test based on your medical history, symptoms, and treatment plan. Regular monitoring may be needed if you have an ongoing condition like an immune disorder or chronic infection.
Can diet or lifestyle affect IgG levels?
While diet and lifestyle factors like stress or poor sleep can influence immune function, they typically do not directly alter IgG levels. However, maintaining a balanced diet rich in vitamins and minerals can support overall immune health.
  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