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Total Serum Immunoglobulin G (IgG) Concentration

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 by fighting bacteria and viruses.

Quick summary

["IgG levels help assess your immune system’s ability to fight infections and respond to vaccines."]

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

Key facts at a glance

LOINC
22556-5
Short code
Deprecated S pneum8 IgG Ser-aCnc
Synonyms
Deprecated S pneum8 IgG 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 Is Done

Your doctor may order this test if you have symptoms of a weakened immune system, such as frequent infections, slow wound healing, or unexplained fatigue. It may also be used to monitor conditions like HIV, certain cancers, or autoimmune diseases that affect antibody production.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm to draw blood, which usually takes a few minutes. If you’re on blood thinners, let your doctor know before the test.

What the Test Results Mean

IgG levels can vary based on age, overall health, and medical conditions. Low levels may indicate an immune deficiency, while very high levels could suggest chronic infections, certain cancers, or overactive immune responses.

Common Conditions Affecting IgG Levels

Low IgG levels might be linked to conditions like Common Variable Immunodeficiency (CVID), HIV/AIDS, or long-term use of certain medications. High IgG levels could be seen in chronic infections (e.g., hepatitis), autoimmune diseases (e.g., lupus), or after receiving blood transfusions.

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 low?
Low IgG levels can result from conditions that impair immune function, such as certain autoimmune diseases, HIV/AIDS, or genetic disorders like CVID. It may also occur in people who have had recent infections or are on long-term immunosuppressive medications.
How long does it take to get IgG test results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will discuss the findings with you during your follow-up visit.
Can IgG levels change with age?
Yes, IgG levels can fluctuate with age. Infants and young children have lower IgG levels compared to adults, as their immune systems are still developing. In older adults, IgG levels may also decline slightly, though this isn’t always clinically significant unless accompanied by symptoms.
  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