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Serum/plasma concentration of immunoglobulin G (IgG) by immunoassay

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 important for long-term immunity.

Quick summary

["IgG levels help assess immune function and identify deficiencies or excesses that may affect your health."]

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

Key facts at a glance

LOINC
94443-9
Short code
HLA-C IgG SerPl FC
Synonyms
HLA-C IgG SerPl FC
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
flow-cytometry
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 this test if you have symptoms of a weakened immune system, such as frequent infections, unusual bruising, or bleeding. It may also be used to monitor conditions like HIV, certain cancers, or immune system disorders, or to check for antibody responses after vaccination.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or vein to draw blood. If you’re taking blood from a finger, it may sting briefly. If you’re concerned about needles, let your healthcare provider know.

What the Test Results Mean

Results are compared to a general range of what’s considered normal for IgG levels in healthy adults. Low levels may indicate immune system issues, while very high levels could suggest conditions like multiple myeloma or chronic infections. Your provider will discuss your specific results with you.

Common Conditions Monitored

IgG testing is often used to diagnose or monitor conditions like immunodeficiency diseases, autoimmune disorders, or infections. It can also help track how well vaccines or treatments are working to boost antibody production.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG is the most abundant antibody in your blood and plays a critical role in fighting off bacteria and viruses. Low IgG levels can weaken your body’s ability to fight infections, while high levels may indicate overactive immune responses or certain cancers. Your provider will use these results to guide treatment or further testing if needed.

Short name

IgG Level

Frequently asked questions

What causes IgG levels to be low?
Low IgG levels can result from conditions like primary immunodeficiency, HIV/AIDS, certain cancers (e.g., lymphoma), or long-term use of medications that suppress the immune system. It may also appear in people with malabsorption issues (e.g., celiac disease) that prevent proper nutrient absorption.
What causes IgG levels to be high?
High IgG levels can be seen in chronic infections (e.g., hepatitis, tuberculosis), autoimmune diseases (e.g., rheumatoid arthritis), or certain cancers (e.g., multiple myeloma). Rarely, it may also occur in response to long-term exposure to toxins or certain medications.
How often should IgG levels be checked?
The frequency depends on your health condition. If you have an immune disorder, your provider may recommend regular monitoring. For people with HIV or other chronic illnesses, IgG testing may be part of ongoing care to track immune function.
  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