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Serum or Plasma Immunoassay for Total Immunoglobulin G (IgG) Concentration

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

This test measures the amount of Immunoglobulin G (IgG), a key protein in your immune system, found in your blood.

Quick summary

["IgG helps protect your body from infections and is important for long-term immunity."]

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

Key facts at a glance

LOINC
14027-7
Short code
HTLV I+II rgp21 Ab SerPl Ql IB
Synonyms
HTLV I+II rgp21 Ab SerPl Ql IB
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ib
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

Why Is This Test Done?

Your healthcare provider may order this test to check for low or high levels of IgG, which can happen due to immune system issues, certain medical conditions, or after treatments like chemotherapy. It’s also used to monitor immune function in people with weakened immune systems, such as those with HIV/AIDS or undergoing organ transplants.

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 blood, similar to a routine blood draw. If you’re on blood thinners, let your provider know before the test.

What to Expect During the Test

The test involves a quick, painless blood draw. You might feel a slight pinch, but most people tolerate it well. The blood is then sent to a lab for analysis.

What the Results Mean

Results are compared to a general reference range for IgG levels. Low levels may suggest immune deficiencies, while very high levels could indicate overactive immune responses or certain diseases. Your provider will discuss these results with you in detail.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: IgG Levels

Short name

IgG Level

Frequently asked questions

What causes low IgG levels?
Low IgG levels can occur due to conditions like primary immunodeficiency, chronic liver disease, malnutrition, or certain autoimmune diseases. It may also appear after treatments that weaken the immune system, such as chemotherapy or long-term steroid use. Your provider will consider your overall health and medical history when interpreting results.
What causes high IgG levels?
High IgG levels are less common but can be seen in conditions like chronic infections, certain cancers (e.g., multiple myeloma), or autoimmune diseases like rheumatoid arthritis. They may also be found in people with long-term inflammation or after vaccination. Your provider will review your symptoms and other test results to determine the cause.
How often should I get this test?
The frequency depends on your health condition and treatment plan. If you have an ongoing medical issue affecting your immune system, your provider may recommend regular monitoring. For example, people with HIV/AIDS or after a transplant might need this test more often than others.
  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