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Immunoglobulin G (IgG) Subclass 1, Serum

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

This test measures the amount of Immunoglobulin G (IgG) subclass 1 in your blood serum. IgG is a type of antibody that helps protect your body from infections.

Quick summary

["IgG1 antibodies play a key role in fighting certain infections and immune responses."]

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

Key facts at a glance

LOINC
22550-8
Short code
Deprecated S pneum6+26 IgG Ser-aCnc
Synonyms
Deprecated S pneum6+26 IgG Ser-aCnc
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 This Test Measure?

IgG1 is one of the four subclasses of Immunoglobulin G (IgG), a type of antibody in your blood. It is primarily involved in defending against bacterial and viral infections. Levels can vary based on immune response, chronic infections, or certain immune system conditions.

Why Might Your Doctor Order This Test?

Your doctor may order this test to evaluate immune function, diagnose or monitor conditions affecting antibody levels, or assess responses to treatments like vaccines or medications that influence antibody production.

Common Conditions Monitored or Diagnosed With This Test

IgG1 subclass levels may be checked in cases of suspected immune deficiencies, chronic infections, autoimmune diseases, or to monitor immune responses to therapies such as monoclonal antibodies.

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. It usually takes a few minutes, and you can resume normal activities afterward.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low IgG1 levels might indicate an immune deficiency or chronic illness affecting antibody production. High levels could suggest an overactive immune response, chronic infections, or certain autoimmune conditions. This test is often part of a broader evaluation rather than a standalone diagnostic tool.

Short name

IgG1 Subclass (Serum)

Frequently asked questions

What causes IgG1 levels to be checked?
IgG1 levels are checked if you have symptoms of immune dysfunction, such as frequent infections, unexplained fatigue, or if you are receiving treatments that influence antibody production (e.g., certain medications or vaccines).
How do IgG1 levels relate to overall immunity?
IgG1 is a critical part of your immune system’s defense against pathogens. While it doesn’t provide a direct overall immunity score, low or abnormal IgG1 levels may signal potential immune weaknesses that require further medical evaluation.
Can diet or lifestyle affect IgG1 levels?
Diet and lifestyle factors like nutrition, stress, and overall health can influence immune function, which may indirectly affect antibody levels. However, IgG1 levels are primarily assessed through blood tests and are not directly influenced by diet alone unless underlying health conditions are present.
  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