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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 plays a key role in long-term immunity.

Quick summary

["IgG antibodies help protect your body from infections and diseases over time."]

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

Key facts at a glance

LOINC
30488-1
Short code
Deprecated S pneum12 IgG sp1 Ser-mCnc
Synonyms
Deprecated S pneum12 IgG sp1 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 helps assess your overall immune response and identify if your body is producing enough IgG to fight infections effectively.

Why Might You Need This Test?

Doctors may order an IgG test if you have symptoms of a weakened immune system, such as frequent infections, delayed healing, or if you’re being treated for conditions like HIV, lupus, or certain autoimmune diseases. It can also be used to monitor immune function before or after treatments like chemotherapy or stem cell transplants.

What to Expect Before the Test

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

What Are Possible Results?

Results are typically reported as a mass concentration (e.g., grams per liter). While reference ranges vary by lab, lower than expected levels may suggest immune deficiency, while higher levels could indicate chronic infections, certain cancers, or other conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

Why was this test ordered?
Your doctor may have ordered this test to evaluate your immune system, diagnose conditions like hypogammaglobulinemia, or monitor treatment progress for immune-related illnesses.
What does a low IgG level mean?
A low IgG level may indicate an immune system that doesn’t produce enough antibodies to fight infections, which can lead to recurrent infections or other health issues. This could be due to genetic disorders, certain medications, or chronic illnesses.
Can IgG levels change over time?
Yes, IgG levels can fluctuate due to infections, vaccinations, aging, or medical treatments. Regular monitoring may be needed if you have a chronic condition or are undergoing treatments that affect immunity.
  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