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IgG Immunoglobulin (Serum) – Mass Concentration

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of IgG antibodies in your blood. IgG is the most common type of antibody and helps protect your body from infections.

Quick summary

["IgG antibodies play a key role in long-term immunity and disease defense."]

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

Key facts at a glance

LOINC
47496-5
Short code
Deprecated S pneum34 IgG sp2 Ser-mCnc
Synonyms
Deprecated S pneum34 IgG sp2 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

What Does IgG Measure?

IgG antibodies are part of your immune system’s defense. They are produced in response to infections, vaccines, and other immune challenges. This test specifically looks at the total amount of IgG in your serum, which can help doctors assess your immune response or identify conditions affecting antibody levels.

Why Might You Need This Test?

Doctors may order an IgG test to evaluate immune function, diagnose conditions like immunodeficiency, check vaccine responses, or monitor chronic illnesses. It can also help identify if you have low or high IgG levels that might affect your health.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw a blood sample. The process is quick and usually painless. If you’re on blood-thinning medication, let your doctor know before the test.

What to Expect After the Test

After the blood is drawn, you can return to your normal activities. There may be a slight bruise or soreness at the site, but this usually goes away within a few days. If you experience excessive bleeding or unusual pain, contact your healthcare provider.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

How Does IgG Relate to Vaccines?
IgG antibodies are produced after vaccination or infection. A doctor may check IgG levels to see if you’ve developed enough antibodies to protect against diseases like measles, chickenpox, or flu. If IgG levels are low, you might need booster shots or additional support to build immunity.
What Conditions Can IgG Levels Help Diagnose?
IgG testing can help diagnose conditions like primary immunodeficiency diseases, certain autoimmune disorders, or chronic infections. For example, low IgG levels might suggest a condition like Common Variable Immunodeficiency (CVID), while high levels could be linked to conditions like chronic lymphocytic leukemia or certain infections.
Can IgG Levels Change Over Time?
Yes, IgG levels can fluctuate depending on your health, immune response, and medical treatments. For example, after an infection or vaccination, IgG levels may rise temporarily. Chronic illnesses or treatments like chemotherapy can also affect IgG levels, so it’s important to discuss any changes with your doctor.
  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