Skip to content

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 is important for fighting infections and providing long-term immunity.

Quick summary

["IgG helps protect your body from infections and long-term immune responses."]

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

Key facts at a glance

LOINC
31638-0
Short code
Deprecated S pneum23 IgG sp2 Ser-aCnc
Synonyms
Deprecated S pneum23 IgG sp2 Ser-aCnc
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 Might Be Ordered

Your healthcare provider may order this test to check for low or high levels of IgG, which can happen due to immune system issues, certain medical conditions, or after treatments like chemotherapy. It may also be used to monitor immune function in people with chronic illnesses or those receiving immune-modifying therapies.

What to Expect Before the Test

No special preparation is usually needed. You may have a small needle inserted into a vein in your arm to draw blood. The process is quick and typically painless. If you’re on blood thinners or have a hard time with needles, let your provider know.

What the Results Mean

IgG levels can vary based on health, age, and other factors. Your results will be compared to a general range provided by your lab. Low IgG might suggest weakened immunity, while very high levels could indicate certain immune disorders or chronic infections.

Common Conditions Monitored

IgG tests are often used to diagnose or monitor conditions like immunodeficiency diseases, autoimmune disorders, chronic infections (e.g., HIV), and certain cancers. They may also help assess immune response after vaccination or treatment for immune-related conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: IgG Levels and Health

Short name

IgG Level

Frequently asked questions

What does a low IgG level mean?
A low IgG level may indicate a weakened immune system, which can make you more susceptible to infections. This could be due to primary immunodeficiency, certain medications, or conditions like HIV/AIDS. It’s important to discuss symptoms like frequent infections, slow wound healing, or recurrent ear/nose/throat infections with your doctor.
What does a high IgG level mean?
High IgG levels can sometimes be a sign of chronic infections, autoimmune diseases (like rheumatoid arthritis), or certain cancers. They may also appear after repeated infections or in response to vaccines. Your doctor will consider your overall health and other test results to interpret these findings.
How often should I get this test?
The frequency depends on your health condition and treatment plan. If you have a chronic illness or are on immune-modifying treatments, your doctor may recommend regular monitoring. Otherwise, this test is often done only when symptoms or concerns suggest it’s needed.
  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