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Immunoglobulin G (IgG) in Serum, Mass Concentration

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

This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood serum. IgG helps protect your body from infections and diseases.

Quick summary

["IgG antibodies play a critical role in long-term immunity."]

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

Key facts at a glance

LOINC
27437-3
Short code
Deprecated S pneum23 IgG sp2 Ser IA-mCnc
Synonyms
Deprecated S pneum23 IgG sp2 Ser IA-mCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 Is IgG Used For?

IgG levels are often checked to assess immune function, monitor conditions like infections, autoimmune diseases, or immune deficiencies, and evaluate responses to treatments. It can also help diagnose or manage certain disorders, such as HIV, hepatitis, or certain cancers.

Why Might You Need This Test?

Your healthcare provider may order this test if you have symptoms of a weakened immune system (like frequent infections), if you’re being treated for an infection or autoimmune condition, or if you’re planning a pregnancy to check for potential immune-related risks.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate the serum, which is sent to the lab for analysis. The test measures the mass concentration of IgG antibodies.

What Do Results Mean?

Results may indicate normal immune function, low levels (hypogammaglobulinemia) that could suggest immune deficiencies, or high levels (hypergammaglobulinemia) that may be linked to chronic infections, autoimmune diseases, 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 might my IgG test result be different from what I expected?
IgG levels can vary based on factors like age, overall health, recent infections, medications, or underlying conditions. For example, newborns have lower IgG levels than adults, and chronic illnesses may affect them differently.
Could my IgG test be affected by what I eat or drink?
Dietary factors like vitamin D, zinc, or protein intake may indirectly support immune function, but they don’t directly influence IgG test results. Avoiding alcohol or certain medications (like steroids) before the test can help ensure accurate results.
What if my IgG test is abnormal?
If your IgG level is low, your doctor may recommend further testing or treatments to support your immune system. If it’s high, they might investigate underlying causes like infections, autoimmune diseases, or other health concerns. Follow-up may include additional blood tests or discussions about lifestyle or treatment adjustments.
  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