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Serum or plasma concentration of immunoglobulin G (IgG) by nephelometry

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 and diseases.

Quick summary

["IgG supports immune function and helps fight infections—low levels may indicate immune deficiency."]

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

Key facts at a glance

LOINC
81774-2
Short code
SMA IgG Ser Ql
Synonyms
SMA IgG 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
CPT
82784
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 Is Done

Your doctor may order an IgG test to check for immune system health, especially if you have frequent infections, certain autoimmune conditions, or are at risk of immune disorders. It can also help diagnose conditions like HIV, certain cancers, or congenital immune deficiencies.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted to draw blood from your arm. If you’re taking blood from a vein in your arm, you might feel a slight pinch, but it usually doesn’t cause discomfort afterward.

What to Expect During the Test

The blood sample is sent to a lab for analysis using a specialized method called nephelometry, which measures the concentration of IgG in your serum or plasma.

Possible Results and Their Meaning

Results may be below, within, or above normal ranges depending on your health. Low IgG levels might suggest a weakened immune system, while very high levels could indicate conditions like multiple myeloma or chronic infections.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG levels are critical for diagnosing and monitoring immune-related conditions. Low IgG can indicate primary immunodeficiency, HIV/AIDS, or other chronic illnesses. High IgG may signal chronic infections, autoimmune diseases, or certain cancers. Regular monitoring helps manage these conditions effectively.

Short name

IgG Level

Frequently asked questions

What causes IgG levels to be low?
Low IgG levels can result from immune system disorders (like primary immunodeficiency), chronic illnesses (such as HIV or liver disease), malnutrition, or certain medications. Rarely, it may be congenital (present from birth).
What causes IgG levels to be high?
High IgG levels are often linked to chronic infections (like tuberculosis or hepatitis), autoimmune diseases (such as lupus or rheumatoid arthritis), or certain cancers (like multiple myeloma). Stress, malnutrition, or long-term use of certain medications may also play a role.
Can IgG levels change over time?
Yes, IgG levels can fluctuate due to infections, treatments, or underlying health conditions. Your doctor may recommend follow-up tests to monitor changes and adjust treatment plans accordingly.
  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