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Immunoglobulin G (IgG) in Serum/Plasma

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 is important for long-term immunity.

Quick summary

["IgG helps fight infections and supports long-term immunity by binding to pathogens."]

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

Key facts at a glance

LOINC
78962-8
Short code
IgG/Transf clear Ur+SerPl-Rto
Synonyms
IgG/Transf clear Ur+SerPl-Rto
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
8
Ref high
61
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82977
SNOMED
3110003
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 Is IgG Used For?

IgG is primarily measured to assess your immune system’s ability to produce antibodies. It can help diagnose or monitor conditions like immune deficiencies, infections, or certain autoimmune diseases. Doctors may also check IgG levels before or after treatments that affect immunity, such as chemotherapy or organ transplants.

Why Might You Need This Test?

Your doctor may order an IgG test if you have symptoms of a weakened immune system (like frequent infections), if you’re being treated for an infection, or if you have a condition that affects antibody production. It can also be used to evaluate immune responses in newborns or during pregnancy.

How Is the Test Performed?

A blood sample is drawn from a vein in your arm. The blood is then processed to separate the serum or plasma, where the IgG antibodies are measured using a specialized lab test. The result is reported as a concentration level, though exact reference ranges vary by lab.

What Do the Results Mean?

Results may be compared to a reference range provided by your healthcare provider. Low IgG levels might suggest an immune deficiency, while very high levels could indicate chronic infections, certain cancers, or other conditions. Always discuss your results with your doctor.

Reference range

Adult males: 8-61 U/L; Adult females: 5-36 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What Causes Low IgG Levels?
Low IgG levels can occur due to conditions like common variable immunodeficiency (CVID), HIV/AIDS, certain cancers (e.g., lymphoma), or long-term use of medications that suppress the immune system. It may also appear in newborns with inherited immune disorders or those born to mothers with certain infections.
What Causes High IgG Levels?
High IgG levels are often seen in chronic infections (e.g., hepatitis, tuberculosis), autoimmune diseases (e.g., rheumatoid arthritis), or certain cancers (e.g., multiple myeloma). Rarely, they may be due to overproduction of antibodies in response to vaccines or allergies.
How Often Should I Get This Test?
Your doctor will determine how often you need this test based on your health condition, treatment plan, or symptoms. Regular monitoring may be needed if you have an ongoing immune-related issue or are receiving treatments that affect antibody levels.
  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