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Serum IgG Substance Concentration (Quantitative Immunoglobulin G Level)

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, which helps fight infections and supports immune function.

Quick summary

["IgG helps protect your body from infections and supports long-term immunity."]

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

Key facts at a glance

LOINC
85954-6
Short code
S pneum Da 1 IgG Ser-mCnc
Synonyms
S pneum Da 1 IgG Ser-mCnc
Category
coagulation
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

Why This Test Is Done

Your healthcare provider may order an IgG test to check for low or high levels, which could indicate conditions like immune deficiencies, infections, or certain autoimmune diseases. It may also be used to monitor treatment responses or diagnose conditions such as HIV, hepatitis, or certain cancers.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if your blood is drawn early in the morning. Bring any medications or supplements you’re taking to discuss with your provider.

How the Test Is Performed

A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a slight sting, but it usually goes away quickly. The blood sample will be sent to a lab for analysis.

What the Results Mean

IgG levels vary depending on age, overall health, and medical conditions. Your results will be compared to a reference range provided by your lab. Low IgG levels may suggest weakened immunity, while very high levels could indicate chronic infections or certain diseases.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG Level

Frequently asked questions

What does low IgG mean?
Low IgG levels may indicate an immune system that isn’t working as well as it should, which can make you more susceptible to infections. This could be due to conditions like primary immunodeficiency, HIV/AIDS, or certain medications that suppress the immune response.
What does high IgG mean?
High IgG levels may suggest chronic infections (such as hepatitis or tuberculosis), autoimmune diseases (like lupus), or long-term exposure to certain substances. Your provider will consider your medical history and other test results to determine the cause.
Can IgG levels change over time?
Yes, IgG levels can fluctuate due to infections, vaccinations, pregnancy, or certain medications. Regular monitoring may be needed if you have a condition that affects your immune system, such as HIV or cancer treatment.
  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