Serum or plasma concentration of immunoglobulin G (IgG) subtypes (IgG1, IgG2, IgG3, IgG4)

Why This Test Might Be Ordered

Your doctor may recommend this test if you have symptoms like frequent infections, unusual immune responses, or conditions such as autoimmune diseases, certain allergies, or immune deficiencies. It could also be part of monitoring for diseases like lupus, rheumatoid arthritis, or other chronic illnesses affecting the immune system.

What to Expect Before the Test

No special preparation is usually needed. You’ll provide a blood sample, typically drawn from your arm. If you’re using blood thinners, let your doctor know to avoid unnecessary bruising.

What the Results Mean

IgG subtypes are measured in mass concentration units (e.g., grams per liter). Abnormal levels may indicate immune system issues, such as too much or too little of a specific subtype, which can affect how well your body fights infections or responds to vaccines.

Common Conditions Linked to IgG Subtype Levels

Low levels of certain IgG subtypes might suggest immune deficiencies or conditions like common variable immunodeficiency (CVID). High levels could be seen in chronic infections, certain autoimmune diseases, or as a side effect of treatments like monoclonal antibodies.