Immunoglobulin G (Igg), Serum

Immunoglobulin G (IgG), Serum

What it is

The Immunoglobulin G (IgG), Serum test measures the level of IgG antibodies in the blood. IgG is the most abundant antibody in the body and plays a key role in long-term immunity after infection or vaccination. It protects against bacterial and viral infections and helps in the recognition and neutralization of pathogens. Abnormal IgG levels may indicate immune deficiencies, chronic infections, autoimmune conditions, or certain blood cancers.

Uses

This test is used to:

• Evaluate overall immune system status and function.
• Identify IgG deficiency, which may cause recurrent infections.
• Detect elevated IgG levels in autoimmune or chronic inflammatory conditions.
• Assist in diagnosing and monitoring multiple myeloma, lymphoma, or other gammopathies.
• Monitor immune response after infections or vaccinations.

Symptoms / Conditions That May Lead to the Test

Doctors may recommend this test if you have:

• Recurrent or severe bacterial and viral infections.
• Unexplained fatigue, chronic inflammation, or autoimmune symptoms.
• Suspicion of immunodeficiency or hypogammaglobulinemia.
• Bone pain, anemia, or abnormal blood tests suggestive of multiple myeloma.
• Need to evaluate vaccine response or immunity status.

Abnormal Results

• Low IgG Levels: May indicate primary or secondary immunodeficiency, protein loss (nephrotic syndrome, GI protein loss), or some genetic immune disorders.
• High IgG Levels: Can occur in chronic infections, autoimmune diseases (e.g., lupus, rheumatoid arthritis), chronic liver disease, or plasma cell disorders such as multiple myeloma.
• Normal IgG Levels: Suggest adequate immune protection, though additional testing may be needed if symptoms persist.

Results are interpreted alongside IgA, IgM, and sometimes IgE levels for a complete immune profile.

Risks

The test requires a blood sample and carries minimal risks, including:

• Mild pain, bruising, or discomfort at the puncture site.
• Rare risk of infection or dizziness after blood draw.