Immunoglobulin A (IgA)

An immunoglobulins test usually measures the three main types of immunoglobulin (Ig) antibodies that your body makes.

IgA is the antibody most active at the surfaces that line your airways, gut, and other body openings, where it helps protect against germs entering through these tissues. Because of this, IgA is also the immunoglobulin most often missing in people with selective immune deficiencies.

You may need this test if you have symptoms of low immunoglobulin production. One of the main symptoms of low immunoglobulin levels is frequent infections, especially repeated infections from the same germ.

Your provider will compare your levels of IgM, IgG, and IgA. Your results can mean different things, depending on your symptoms, any conditions you may have, and which immunoglobulins are high or low. An immunoglobulins blood test alone cannot diagnose any conditions. So if your results aren't normal, you'll probably need more testing to find out what's affecting your immune system.

Higher than normal IgA may be seen with chronic liver disease (such as hepatitis or cirrhosis), some long-lasting infections, autoimmune conditions, and rarely a type of multiple myeloma where plasma cells make extra IgA. A very high level driven by a single "clone" of plasma cells may need more tests, including blood and urine protein studies.

Lower than normal IgA may be a sign of a primary immune deficiency such as selective IgA deficiency or common variable immunodeficiency, or it can happen with kidney problems that lose protein, severe burns, malnutrition, or certain medicines.

If your immunoglobulin levels aren't normal, it doesn't always mean you have a condition that needs treatment. Certain medicines can affect your results. If you have questions about your results, talk with your provider. The earlier you start treating abnormal immunoglobulin levels, the more likely you are to treat its underlying cause.