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Serum Immunoglobulin G (IgG) Level

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 and diseases.

Quick summary

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

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

Key facts at a glance

LOINC
41012-6
Short code
RSV IgG Ser Ql
Synonyms
RSV IgG Ser Ql
Category
chemistry
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 This Test Measure?

IgG is the most abundant antibody in your blood and is crucial for defending against bacteria and viruses. Your body produces IgG in response to infections or vaccines. This test helps doctors assess your immune system’s ability to fight infections and monitor conditions like immunodeficiency or chronic illnesses.

Why Might You Need This Test?

Doctors may order an IgG test to evaluate your immune response, diagnose conditions like HIV, lupus, or other autoimmune diseases, or check for deficiencies in antibody production. It’s also used in newborns to assess maternal antibody transfer and in patients receiving immune-suppressing treatments.

When Is This Test Done?

A blood sample is taken from a vein in your arm. The sample is sent to a lab, where it is analyzed using an immunoassay method to measure IgG levels. Results are typically available within a few days.

What Are Common Reasons for Testing?

Common reasons include diagnosing or monitoring immune-related conditions, evaluating symptoms like frequent infections, or checking for immune system dysfunction. It may also be used in research or clinical trials involving immune responses.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG levels can help identify immune system strengths or weaknesses. Low IgG levels may indicate a weakened immune response, while high levels could suggest chronic infections, autoimmune diseases, or overactive immune reactions. This test is not diagnostic for specific conditions alone but provides critical information for further evaluation.

Short name

IgG Level

Frequently asked questions

Why might my IgG levels be checked regularly?
If you have a condition like HIV, lupus, or are undergoing treatments that suppress your immune system (e.g., chemotherapy), your doctor may monitor IgG levels to ensure your immune response remains adequate. Regular checks help prevent infections and manage your treatment plan.
What do my IgG results mean?
Results are compared to a general reference range, but your doctor will interpret them in the context of your overall health, symptoms, and medical history. Low IgG may raise concerns about immune function, while very high levels could indicate chronic infections or other underlying issues. Your doctor will discuss findings with you.
Can diet or lifestyle affect IgG levels?
Diet and lifestyle factors like nutrition, stress, and smoking can influence immune function indirectly, but they do not directly alter IgG levels. Maintaining a balanced diet, staying hydrated, and managing stress can support overall immune health, though IgG testing focuses specifically on 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