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Serum Immunoglobulin G (IgG) Level

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

This test measures the amount of Immunoglobulin G (IgG) in your blood. IgG is the most common type of antibody in your body and helps protect you from infections.

Quick summary

["IgG antibodies play a key role in long-term immunity."]

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

Key facts at a glance

LOINC
108794-9
Short code
Septin-5 IgG Msmt SerPl
Synonyms
Septin-5 IgG Msmt SerPl
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85610
SNOMED
396252006
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 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 after organ transplants.

What to Expect During the Test

A blood sample will be taken from a vein, usually in your arm. You may feel a slight pinch, but it shouldn’t cause significant discomfort. The test involves drawing a small amount of blood, which is then sent to a lab for analysis.

Preparation for the Test

No special preparation is needed for this test. However, if you’re taking certain medications or have a history of bleeding disorders, your provider may give you specific instructions.

Possible Results and Their Meaning

IgG levels can vary based on age, overall health, and medical conditions. Low IgG levels may suggest a weakened immune system, while very high levels could indicate chronic infections, autoimmune diseases, or certain cancers. Your results will be discussed with you by your healthcare provider.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: serum

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What might cause abnormal IgG levels?
Abnormally low IgG levels can occur in conditions like hypogammaglobulinemia (a rare immune disorder), HIV/AIDS, or after certain treatments that weaken the immune system. High IgG levels may be seen in chronic infections, autoimmune diseases (like lupus), or in response to certain vaccines.
How often will I need this test?
The frequency of this test depends on your health condition and treatment plan. Your healthcare provider will determine how often you need it based on your individual needs and medical history.
Can I eat or drink before this test?
You can eat and drink normally before this test, as it doesn’t require fasting. However, always follow any specific instructions your healthcare provider gives you.
  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