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Immunoglobulin G (IgG) Subclass 1 (Serum) – Quantitative

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

This test measures the amount of a specific type of antibody (IgG1) in your blood, which plays a key role in fighting infections and providing long-term immunity.

Quick summary

["IgG1 helps your immune system respond to certain pathogens and is often checked if you have immune-related conditions or need monitoring for antibody levels."]

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

Key facts at a glance

LOINC
107067-1
Short code
NKCT
Synonyms
CD19-CD3-CD56+ (NK) NFr Bld FC
Category
chemistry
Sample
whole-blood
Container
EDTA (lavender/purple-top) or ACD (yellow-top) anticoagulated tube; sodium heparin (green-top) tube is also acceptable for flow cytometry applications.
Units
N/A
Ref low
5
Ref high
20
Fasting
false
Population
adult
Sex
all
Age range
0–99 years
Method
flow-cytometry
CPT
86359
SNOMED
416996001
Specimen volume
Minimum 1-3 mL of whole blood; 3-5 mL preferred for adequate lymphocyte yield and reliable subset enumeration.
Stability
Specimen should be processed within 24-48 hours of collection when stored at room temperature (18-25°C). Do not refrigerate as cold-induced apoptosis may affect lymphocyte viability. Samples older than 48 hours should be rejected.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
24–72 hours
Order
routine

What Does This Test Measure?

IgG1 is one of four subclasses of Immunoglobulin G (IgG), a type of antibody that your immune system produces to defend against bacteria and viruses. This test specifically quantifies the concentration of IgG1 in your serum, which can vary depending on your immune response, health status, or medical treatment.

Why Might You Need This Test?

Doctors may order this test if you have conditions like autoimmune diseases, infections, or certain immune deficiencies. It can also be used to monitor treatment responses, such as in patients receiving immunotherapy or those with chronic illnesses like HIV or lupus.

Common Reasons for Testing

Common reasons include diagnosing or managing immune disorders, evaluating immune function in patients with recurrent infections, or assessing antibody levels before or after vaccination to ensure proper immune response.

Sample Collection and Preparation

A blood sample is drawn from a vein, typically in your arm, and sent to the lab for processing. The serum (liquid part of blood after clotting) is then analyzed to measure IgG1 levels.

Reference range

NK cells (CD3- CD19- CD56+) typically represent 5-20% of total lymphocytes; absolute count approximately 100-600 cells/µL in healthy adults. Reference ranges vary by laboratory and instrumentation.N/A

Specimen: whole-blood

No fasting required. Avoid strenuous exercise prior to collection as it may transiently alter lymphocyte subset distribution. Patients should be well-hydrated. Recent corticosteroid therapy, chemotherapy, or immunosuppressive medications should be noted as they may affect NK cell counts.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG1 Level

Frequently asked questions

IgG1 levels can be lower than expected in people with certain immune deficiencies or autoimmune diseases, which may affect their ability to fight infections. Conversely, elevated levels might indicate chronic inflammation, certain infections, or overactive immune responses.
IgG1 levels are not typically used alone to diagnose conditions but can provide important context when combined with clinical findings and other tests. For example, low IgG1 might suggest a specific type of immune dysfunction that requires further investigation.
What do abnormal IgG1 levels mean?
Abnormal IgG1 levels may signal underlying health issues, such as an immune system that is too weak (hypogammaglobulinemia) or too active (autoimmune disease). Your doctor will discuss these results in the context of your medical history and other test results.
How often should I get this test?
The frequency depends on your medical condition and treatment plan. Your healthcare provider will determine how often to check IgG1 levels, often as part of a broader monitoring strategy for chronic illnesses or immune-related treatments.
  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