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Serum Immunoglobulin G (IgG) concentration

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

This test measures the amount of Immunoglobulin G (IgG), the most common type of antibody in your blood. IgG helps protect your body from infections by fighting bacteria and viruses.

Quick summary

["IgG antibodies play a key role in long-term immunity and are often checked if you have recurring infections or immune system concerns."]

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

Key facts at a glance

LOINC
43301-1
Short code
HTLV I+II p36 Ab Ser Ql
Synonyms
HTLV I+II p36 Ab Ser Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like frequent infections, low energy, or if you’re being treated for an immune-related condition. It can also be part of monitoring for conditions like HIV, lupus, or certain cancers.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm to draw blood. It usually takes a few minutes, and you may feel a slight pinch. Avoid heavy exercise or eating for 2 hours before the test if instructed.

What the Results Mean

Results are compared to a general range for healthy adults, but individual ranges can vary. Low IgG levels may suggest weakened immunity, while very high levels might indicate certain immune disorders or chronic infections.

Common Conditions Monitored

IgG levels are often checked in people with chronic illnesses, those receiving immune-suppressing treatments, or those with a history of frequent infections. It can also help diagnose or manage conditions like HIV, autoimmune diseases, or certain cancers.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG Level

Frequently asked questions

What Does a Low IgG Level Indicate?
Low IgG levels may indicate a weakened immune system, which can make you more susceptible to infections. This could be due to conditions like HIV/AIDS, certain autoimmune diseases, or malnutrition. Your doctor may recommend additional tests or treatments to support your immune function.
What Does a High IgG Level Indicate?
High IgG levels can sometimes signal chronic infections, certain autoimmune diseases (like lupus or rheumatoid arthritis), or long-term exposure to allergens. In some cases, it may also be a side effect of certain medications or immune system overactivity.
How Often Should I Get This Test?
The frequency depends on your health status. If you have a chronic condition, your doctor may order this test regularly to monitor your immune function. If you’re healthy, it’s usually not routine unless symptoms or risk factors suggest it.
  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