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Immunoglobulin G (IgG) in Serum

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 diseases.

Quick summary

["IgG antibodies play a critical role in long-term immunity by fighting bacteria and viruses."]

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

Key facts at a glance

LOINC
32850-0
Short code
Deprecated S pneum5 IgG Ser IA-mCnc
Synonyms
Deprecated S pneum5 IgG Ser IA-mCnc
Category
coagulation
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

Why This Test Might Be Ordered

Your healthcare provider may order an IgG test to check for low or high levels, which can happen due to immune system issues, chronic illnesses, or certain medical conditions. It may also be used to monitor treatment responses, such as in autoimmune diseases or after receiving certain vaccines.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood, and you’ll rest for a few minutes afterward. If you’re on blood thinners, let your provider know before the test.

What the Results Mean

IgG levels can vary based on age, overall health, and medical conditions. While reference ranges differ by lab, very low IgG levels may suggest immune deficiencies, while very high levels could indicate chronic infections, autoimmune disorders, or other health concerns.

Common Conditions Monitored

IgG tests are often used to diagnose or monitor conditions like HIV, chronic infections (e.g., hepatitis), autoimmune diseases (e.g., lupus), or immune system disorders (e.g., severe combined immunodeficiency). They may also help assess vaccine responses.

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 too low?
Low IgG levels can result from conditions that weaken the immune system, such as HIV/AIDS, certain cancers, or genetic disorders like Common Variable Immunodeficiency (CVID). Chronic illnesses like kidney disease or malnutrition may also lead to lower IgG. Rarely, medications or certain treatments can affect antibody production.
What causes IgG levels to be too high?
High IgG levels can occur with chronic infections (e.g., tuberculosis, hepatitis), autoimmune diseases (e.g., rheumatoid arthritis), or in response to repeated vaccinations. Some cancers, like multiple myeloma, may also elevate IgG. In some cases, the body may produce excessive antibodies due to unknown reasons.
How often should IgG levels be checked?
The frequency of IgG testing depends on your medical condition. If you have an immune disorder, your doctor may recommend regular monitoring. For example, people with HIV or CVID might check IgG levels every few months. Always follow your healthcare provider’s advice.
  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