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Total Immunoglobulin G (IgG) in Serum

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 role in immune response.

Quick summary

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

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

Key facts at a glance

LOINC
5255-5
Short code
M pneumo IgG Ser IA-aCnc
Synonyms
M pneumo IgG Ser 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 a type of antibody produced by your immune system to help fight infections. Your body makes IgG in response to pathogens like bacteria and viruses. This test checks the total amount of IgG in your serum, which can help doctors assess your immune system’s strength or identify issues like low immunity.

Why Might You Need This Test?

Doctors 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 cancers, or autoimmune diseases.

Sample Collection and Preparation

A blood sample is drawn from a vein in your arm. The blood is then separated into serum (the liquid part after clotting) to measure IgG levels. This test is typically done in a lab using an immunoassay method to detect and quantify IgG accurately.

When Results Might Be Abnormal

Results can vary based on your health, age, and other factors. Very low IgG levels may suggest an immune deficiency, while very high levels could indicate conditions like multiple myeloma or chronic infections. Your doctor will interpret results in the context of your overall health.

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 change?
IgG levels can change due to infections, immune system conditions (like HIV or autoimmune diseases), certain medications, or genetic factors. Frequent infections, poor nutrition, or chronic illnesses may also affect IgG levels.
How long does it take to get results?
Results are usually available within 1 to 3 business days, depending on your lab’s processing time. Your doctor will contact you with the findings once they’re ready.
Can lifestyle changes affect IgG levels?
Yes, diet, stress, and overall health can influence IgG levels. Eating a balanced diet rich in vitamins and proteins may support immune function, but IgG levels are primarily determined by your immune system’s response.
  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