What Do Low IgA Levels Mean, and Is IgA Deficiency Serious?

Low IgA levels mean your blood has less immunoglobulin A, an antibody that helps protect the linings of the airways, eyes, mouth and gut, than your laboratory's range. When IgA is low or absent but other antibodies are normal, it is called selective IgA deficiency. It is often found by chance, and many people with it never have symptoms.

This guide explains why low IgA is often harmless, when it matters, and how it can affect coeliac disease testing. It cannot tell you whether your own result is significant; that depends on the full results and your history.

MedlinePlus advises people with IgA deficiency to contact a healthcare provider if they have signs of infection or gut symptoms. Arrange a prompt review if you notice:

• Infections that keep coming back, such as sinus, ear, chest or eye infections.
• Pneumonia, or an infection that is not improving with the usual treatment.
• Diarrhoea that lasts, or gut symptoms with weight loss.
• New joint pain, rashes or other symptoms that could suggest an autoimmune condition.
• For sudden severe illness, such as trouble breathing or confusion, use your local emergency number.

MedlinePlus gives a typical adult IgA range of 103 to 501 mg/dL (about 1.0 to 5.0 g/L). Ranges vary between laboratories and units differ, so compare your result with the range printed on your own report.

Ask whether IgG and IgM were measured at the same time. Low IgA on its own points in a different direction from low IgA together with low IgG, which can be part of broader antibody deficiencies such as common variable immune deficiency. Your clinician will interpret the pattern, not just one number.

Usually not. MedlinePlus describes it as the most common immune deficiency disorder, and Cleveland Clinic calls it the mildest form of primary immunodeficiency, estimating it affects about 1 in 500 people of European ancestry. Cleveland Clinic notes that most people with it do not experience complications.

When symptoms do occur, they can include repeated sinus, ear, chest, eye and upper airway infections, and chronic diarrhoea. Allergies, asthma and some autoimmune conditions, including rheumatoid arthritis, lupus and coeliac disease, are more common. There is no treatment that raises IgA itself; care focuses on treating infections and any related conditions.

Cleveland Clinic notes that some children with low IgA begin making normal amounts as they grow, although this is not guaranteed. If a child's result was low, ask whether and when it should be repeated.

Selective IgA deficiency is usually inherited, but it is not the only reason for a low result. Cleveland Clinic and MedlinePlus note that some medicines, including certain immune-suppressing and anti-seizure medicines, have been linked to low IgA. If a medicine might be involved, raise it with the prescriber rather than stopping it yourself.

MedlinePlus also lists gut diseases that cause protein loss, multiple myeloma and, very rarely, agammaglobulinaemia, in which all antibody levels are very low. These are less common explanations, and further tests are needed to confirm or rule out any of them. This is another reason to look at IgA alongside IgG, IgM and your symptoms.

The most common coeliac screening test, tTG-IgA, looks for IgA antibodies against tissue transglutaminase. Cleveland Clinic explains that if your IgA is already low, this test can give a false negative, meaning coeliac disease could be missed. Coeliac disease is also more common in people with IgA deficiency, so this matters.

MedlinePlus notes that labs can check for IgA deficiency as part of coeliac screening, and that other antibody tests, such as deamidated gliadin peptide (DGP) antibodies, are often used when IgA is low. Ask which test was done and whether it can be interpreted with your IgA level.

Blood tests are a first step only. Healthdirect describes coeliac blood testing as a screening test, with a positive result usually confirmed by a small bowel biopsy taken during a gastroscopy. Ask your clinician how your IgA result changes that pathway for you.

Keep eating gluten until testing is complete unless your clinician advises otherwise. MedlinePlus and Healthdirect both say that cutting out gluten before testing can make the results less accurate. If you have had a negative coeliac test and still have symptoms, see the related guide below.

MedlinePlus explains that some people with IgA deficiency develop antibodies against IgA. They can then have severe, even life-threatening reactions to blood products or immunoglobulin treatments. Products with IgA removed can be given safely.

Not everyone with low IgA has these antibodies. Still, tell any hospital team about your result before a planned transfusion or immunoglobulin treatment, and ask whether it should be added to your medical record or alert card.

Bring the full antibody report with dates, earlier results if you have them, a list of medicines, and a note of infections and gut symptoms over the past year.

• Is my IgA low or completely absent, and were my IgG and IgM normal?
• Do my symptoms suggest this is affecting me, or is it likely an incidental finding?
• If I had a coeliac blood test, was it interpreted with my IgA level, and do I need an IgG-based test?
• Should I see an immunologist, and would further tests such as vaccine responses help?
• Should this result be flagged on my record for blood transfusions?
• Is a repeat test needed, and when?

On SameCase, patients and verified doctors share de-identified cases. Seeing how others with low IgA were followed up, for example when a coeliac test was repeated with an IgG-based method, can help you organise your own questions before an appointment.

Other people's cases cannot show whether your result matters or what you have. We suggest using them to prepare questions, then letting your own clinician interpret your results.