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Serum Immunoglobulin G (IgG) Level

Published: August 9, 2026Updated: August 15, 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 is one of the most common antibodies found in serum.

Quick summary

["IgG helps fight infections and supports long-term immunity."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
32858-3
Short code
IGGCELLS
Synonyms
Cells IgG NFr Spec
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) or red-top serum collection tube; alternatively, EDTA or heparinized whole blood for cell-based assays
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
flow cytometry immunophenotyping with fluorescent-labeled anti-IgG antibodies
CPT
86356 (if monoclonal antibody flow cytometry); 88184-88185 may apply depending on assay configuration
SNOMED
313226001 (Immunoglobulin G measurement); 24891006 (Mononuclear cell analysis)
Specimen volume
1-5 mL of whole blood; minimum 500 microliters of serum for cell-free testing
Stability
Whole blood: 24-48 hours at 2-8°C; processed cells: 6-24 hours at 2-8°C; fixed cells: up to 7 days at 2-8°C
Hemolysis max
100
Lipemia max
200
Icterus max
50
TAT
24–72 hours
Order
routine

What Is Immunoglobulin G (IgG)?

IgG is the most abundant type of antibody in your blood. Antibodies are proteins that help your immune system recognize and fight off harmful substances like bacteria and viruses. IgG is particularly important for providing long-term protection against infections and plays a role in defending against diseases that can spread through the bloodstream, such as some types of pneumonia or meningitis.

Why Might You Need This Test?

Your doctor may order an IgG test to check for low or high levels, which can indicate underlying health conditions. Low IgG levels might suggest a weakened immune system, while high levels could be linked to certain autoimmune diseases, chronic infections, or other medical conditions. It may also be used in the evaluation of immune-related disorders or to monitor treatment responses.

When Is This Test Typically Done?

This test is often performed as part of a general health checkup, to diagnose or monitor conditions affecting the immune system, or to assess the effectiveness of treatments for diseases like HIV, lupus, or other autoimmune disorders. It can also be done during pregnancy to check for potential immune-related issues in the mother or fetus.

What Does the Test Involve?

A blood sample is taken from a vein, usually in your arm. The blood is then sent to a lab where it is processed to measure the IgG antibody levels. The results are compared to standard reference ranges to determine if your levels are within normal limits or if further investigation is needed.

Reference range

Reported as percentage of cells positive for intracellular/surface IgG relative to total lymphocyte or leukocyte count; reference intervals vary by cell population analyzed (e.g., IgG+ B-lymphocytes, IgG-bearing lymphocytes)N/A

Specimen: serum

No fasting required. Patient should inform clinician of any recent immunosuppressive therapy, immunoglobulin infusion, or vaccination, as these may influence IgG-expressing cell populations

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What causes low IgG levels?
Low IgG levels can be caused by conditions that affect your immune system, such as primary immunodeficiency diseases, chronic liver disease, certain cancers (like lymphoma), or long-term use of certain medications that suppress the immune system. It may also occur in people with malabsorption issues or those who have undergone organ transplants.
What causes high IgG levels?
High IgG levels can result from chronic infections, autoimmune diseases like rheumatoid arthritis or lupus, certain types of cancer (such as multiple myeloma), or long-term exposure to inflammatory conditions. In some cases, high IgG levels may be a normal part of the immune response to repeated or ongoing infections.
How often should I get this test?
The frequency of IgG testing depends on your medical condition and overall health. If you have an immune-related disorder, your doctor may recommend regular monitoring. Otherwise, this test is usually performed only when there is a specific reason to check your IgG levels, such as symptoms of infection, immune dysfunction, or during pregnancy.
  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 15, 2026. · Read our editorial policy