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Immunoglobulin G (IgG) Subclass 1, Serum

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

This test measures the amount of a specific type of antibody (IgG1) in your blood serum, which plays a key role in fighting infections and certain diseases.

Quick summary

["IgG1 antibodies help protect your body against bacteria, viruses, and toxins."]

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

Key facts at a glance

LOINC
8029-1
Short code
Deprecated S pneum9 IgG Ser IA-aCnc
Synonyms
Deprecated S pneum9 IgG Ser IA-aCnc
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 Does This Test Measure?

IgG1 is one of five subclasses of Immunoglobulin G (IgG), the most abundant antibody in your blood. It is primarily involved in neutralizing pathogens (like bacteria and viruses) and marking them for destruction by other immune cells. Levels can vary depending on your immune response, health status, and certain medical conditions.

Why Might Your Doctor Order This Test?

Your doctor may request this test to evaluate your immune system function, diagnose or monitor conditions like autoimmune diseases, infections, or certain immune deficiencies. It can also help assess how well your body is responding to treatments for diseases that affect antibody production.

Common Conditions Monitored or Diagnosed With This Test

IgG1 levels may be checked in cases of suspected immunodeficiency, autoimmune disorders (such as lupus or rheumatoid arthritis), chronic infections, or to monitor immune responses in patients receiving immunosuppressive therapies.

What to Expect Before the Test

No special preparation is usually needed. You may have a small needle inserted into a vein (typically in your arm) to draw blood. If you’re nervous, let your healthcare provider know so they can help make the process more comfortable.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG1 Subclass (Serum)

Frequently asked questions

How does IgG1 testing help doctors?
IgG1 testing helps doctors understand your immune response. Low levels might indicate an immune deficiency or chronic illness, while abnormal high levels could suggest an overactive immune response or certain autoimmune conditions. This information aids in diagnosing and managing health conditions.
What does it mean if my IgG1 levels are low?
Low IgG1 levels may suggest an impaired immune system, which could be due to genetic disorders, chronic illnesses, or treatments that suppress immune function. Your doctor will consider other factors, such as your medical history and symptoms, to determine the cause and next steps.
Can IgG1 levels change over time?
Yes, IgG1 levels can fluctuate due to infections, vaccinations, or medical treatments. Repeated testing may be needed to monitor changes in immune function, especially in patients with chronic conditions or those undergoing treatment for immune-related diseases.
  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