IgA Blood Test: High, Low, Normal Range, Mucosal Immunity, and Celiac Disease

An IgA blood test measures immunoglobulin A, an antibody that helps protect the body’s moist surfaces, including the airways, digestive tract, eyes, and mouth. The result can help explain repeated sinus, lung, or intestinal infections; support an immune-deficiency evaluation; and prevent misleading celiac disease blood-test results. A low value may reflect selective IgA deficiency, a broader antibody disorder, medication effects, or another illness. A high value more often points to ongoing immune stimulation, such as chronic inflammation, infection, liver disease, or an abnormal population of antibody-producing cells. One result rarely identifies the cause by itself. Age, symptoms, other immunoglobulins, liver and kidney findings, and the pattern on protein studies all shape the interpretation. Because laboratories use different methods and reference intervals, the range printed beside the result is more important than a single “universal” cutoff.

• A common adult IgA reference range is about 60–400 mg/dL, but laboratory and age-specific ranges vary.
• Selective IgA deficiency is generally defined as IgA below 7 mg/dL in a person older than 4 years with normal IgG and IgM after other causes are excluded.
• Low IgA can make tTG-IgA and other IgA-based celiac tests falsely negative, so total IgA should be checked during celiac screening.
• High IgA may occur with chronic liver disease, infection, autoimmune inflammation, IgA nephropathy, or a monoclonal plasma-cell disorder.
• No fasting is usually required, but recent immune-globulin treatment, certain medicines, and acute illness can affect interpretation.
• Urgent care depends on symptoms—not the IgA number alone—such as trouble breathing, severe infection, kidney warning signs, or a transfusion reaction.

Table of Contents

• What the IgA Test Measures
• Normal Range and Testing Details
• What Low IgA Can Mean
• What High IgA Can Mean
• IgA and Celiac Disease Testing
• Follow-Up Tests and Result Patterns
• Next Steps and When to Seek Care

What the IgA Test Measures

The test measures the concentration of IgA in serum, the liquid portion of blood. IgA is one of five major immunoglobulin classes, along with IgG, IgM, IgE, and IgD. Plasma cells—mature immune cells derived from B lymphocytes—produce these antibodies after the immune system encounters microbes, vaccines, food proteins, or other antigens.

Serum IgA is only part of the body’s IgA supply. Most IgA is made near mucosal surfaces and released into secretions such as saliva, tears, airway mucus, intestinal fluid, and breast milk. At these sites, two IgA molecules often join together as secretory IgA. This form can neutralize viruses, toxins, and bacteria before they cross the lining of the respiratory or digestive tract. It also helps keep the gut microbiome in balance without provoking unnecessary inflammation against harmless organisms.

A routine blood test does not directly measure secretory IgA in the nose, lungs, or intestine. Serum and mucosal IgA are related, but they are not interchangeable. A person with very low serum IgA usually has reduced secretory IgA as well, yet symptoms can vary widely because IgM and other immune defenses may partly compensate.

Doctors commonly order IgA as part of an immunoglobulin panel rather than by itself. Comparing IgA with IgG and IgM helps separate an isolated IgA problem from a broader antibody-production disorder. Testing may be considered for:

• Repeated sinus infections, ear infections, bronchitis, or pneumonia
• Chronic diarrhea, giardiasis, unexplained weight loss, or malabsorption
• Suspected celiac disease, especially when an IgA-based antibody test is negative despite strong symptoms
• Autoimmune disease, chronic liver disease, or persistent inflammation
• An unexplained increase in total protein or globulin
• A possible monoclonal gammopathy, lymphoma, or plasma-cell disorder
• Follow-up of a previously abnormal immunoglobulin result

An IgA level is a quantity, not a test of antibody quality. A person can have a normal total IgA concentration but still make weak antibodies to specific bacteria or vaccines. Conversely, a low total IgA level does not automatically mean severe immune failure. Clinical history remains essential.

IgA also has two subclasses. IgA1 makes up most IgA in blood and is common in the upper respiratory tract, while IgA2 is relatively more prominent in the lower intestinal tract, where it is better suited to withstand bacterial enzymes. Routine quantitative IgA testing combines these subclasses and does not report them separately. Subclass testing is rarely needed for an initial evaluation because the total concentration, infection pattern, and other immune studies usually provide more useful information.

Laboratories generally measure IgA with nephelometry or turbidimetry. In both methods, antibodies in the reagent bind the patient’s IgA and form particles that scatter light. The amount of scattered light is converted into a concentration. Very unusual protein patterns, severe lipemia, or a monoclonal protein can occasionally create analytical concerns, so a laboratory may dilute and rerun the specimen or use another method when the result does not fit the clinical picture.

The blood level also cannot show exactly where mucosal defense is failing. Recurrent sinus infections may involve anatomy, allergies, ciliary function, or exposure as well as antibodies. Chronic diarrhea may arise from infection, celiac disease, inflammatory bowel disease, medication effects, or pancreatic problems. IgA is therefore one piece of an organ-specific evaluation rather than a stand-alone explanation for every mucosal symptom.

Normal Range and Testing Details

Adult reference intervals often fall near 60–400 mg/dL, although some laboratories use limits such as 70–400 mg/dL, 85–499 mg/dL, or values reported in grams per liter. To convert units, 100 mg/dL equals 1 g/L. The correct interpretation uses the range printed on the report because analyzer calibration, antibodies used in the assay, and the laboratory’s reference population can differ.

Children require age-specific ranges. IgA is low at birth and rises gradually through childhood. An adult cutoff applied to a toddler could incorrectly label a normal developmental value as deficient. This is one reason selective IgA deficiency is not formally diagnosed before age 4; some younger children simply have delayed maturation of IgA production.

Result pattern	General interpretation	Important caution
Within the laboratory range	Serum IgA quantity is typical for that age and method	Does not rule out a specific-antibody defect, celiac disease, or every immune disorder
Below range but detectable	Partial IgA deficiency, temporary suppression, medication effect, protein loss, or broader immune disorder may be considered	Repeat testing and comparison with IgG and IgM may be needed
Below 7 mg/dL after age 4	May meet the laboratory threshold for selective IgA deficiency	IgG and IgM should be normal, and secondary causes must be excluded
Above range	Usually reflects increased antibody production from inflammation, infection, liver disease, or another immune stimulus	The distinction between polyclonal and monoclonal elevation is more useful than the degree alone

The sample is drawn from a vein. Fasting is usually unnecessary, and time of day has little practical effect. Staying hydrated can make the blood draw easier, but drinking extra water does not meaningfully “normalize” IgA.

Several details can influence interpretation:

• Acute illness: A recent or current infection can raise immunoglobulins, so a mild elevation may be repeated after recovery.
• Medications: Some antiseizure medicines, immune-suppressing drugs, disease-modifying antirheumatic drugs, and B-cell-depleting treatments can lower immunoglobulins. The medication should not be stopped without medical advice.
• Immune-globulin therapy: Intravenous or subcutaneous immune globulin mainly contains IgG but can alter protein studies and complicate interpretation.
• Protein loss: Kidney or intestinal protein loss may reduce several blood proteins, including immunoglobulins.
• Hydration: Severe dehydration can concentrate blood proteins; substantial fluid overload can dilute them.

A single result slightly outside range often deserves context and, when appropriate, confirmation rather than an immediate diagnosis.

What Low IgA Can Mean

Low IgA ranges from a modest age-adjusted reduction to an undetectable level. The most recognized cause is selective IgA deficiency, but the word “selective” has a specific meaning: IgA is profoundly low while IgG and IgM remain normal, vaccine responses are generally preserved, the person is older than 4, and other explanations have been ruled out.

Many people with selective IgA deficiency never develop symptoms. Others have recurrent infections where IgA normally provides front-line protection. Typical patterns include repeated bacterial sinusitis, ear infections, bronchitis, pneumonia, or prolonged gastrointestinal infections. Giardia can cause recurring diarrhea, bloating, and malabsorption. Some people develop asthma, allergic rhinitis, eczema, food allergy, or autoimmune conditions such as celiac disease, thyroid disease, rheumatoid arthritis, or lupus.

Low IgA alone does not establish why infections occur. More severe or unusual infections may point to an additional problem, such as an IgG subclass deficiency, impaired vaccine responses, low lymphocyte counts, or common variable immunodeficiency. A broader primary immunodeficiency blood test panel may include quantitative immunoglobulins, lymphocyte subsets, complement studies, and functional antibody testing.

Other causes of low IgA include:

• Broader antibody deficiency: IgG may also be low in common variable immunodeficiency or medication-related hypogammaglobulinemia.
• Medications and treatment: Rituximab and other B-cell-depleting therapies, some anticonvulsants, immune suppressants, and certain antirheumatic drugs may reduce antibody production.
• Blood cancers: Chronic lymphocytic leukemia, lymphoma, or myeloma can suppress normal immunoglobulins.
• Protein loss: Nephrotic syndrome, protein-losing enteropathy, severe burns, or extensive skin disease may lower multiple proteins.
• Inherited syndromes: Ataxia-telangiectasia, Wiskott-Aldrich syndrome, hyper-IgM syndromes, and other genetic immune disorders may include low IgA.
• Temporary or age-related findings: Young children may have delayed IgA maturation, and transient reductions can occur during illness or after certain treatments.

Selective IgA deficiency does not have a replacement treatment equivalent to standard IgG replacement because routine immune-globulin products contain little IgA and are not given simply to correct the number. Management focuses on treating infections promptly, assessing vaccine responses when clinically indicated, managing associated allergies or autoimmune disease, and protecting lung health if infections are recurrent.

A small subset of people with profound IgA deficiency form anti-IgA antibodies. Severe allergic reactions to transfused plasma-containing products are rare, but a history of a previous transfusion reaction is important. People with confirmed profound deficiency and a concerning reaction history should tell clinicians and blood-bank staff before transfusion. Washed red cells or specially selected products may be considered by the treating team.

What High IgA Can Mean

High IgA usually means that groups of plasma cells are producing more antibody in response to persistent immune stimulation. The result is often polyclonal, meaning many different antibody-producing cell families are active. Polyclonal elevation commonly accompanies chronic liver disease, autoimmune inflammation, long-lasting infection, inflammatory bowel disease, some lung diseases, and other inflammatory states.

Liver disease is an important association. IgA may rise in alcohol-related liver disease, cirrhosis, and metabolic dysfunction-associated steatotic liver disease, especially as fibrosis advances. The IgA value cannot diagnose liver disease or determine its stage, but an elevation alongside abnormal liver enzymes, low platelets, high bilirubin, or imaging changes may support further evaluation.

Other possible associations include:

• Chronic respiratory, gastrointestinal, or other infections
• Rheumatoid arthritis, lupus, inflammatory bowel disease, and some vasculitides
• IgA nephropathy and IgA vasculitis
• Chronic skin or lung inflammation
• Obesity and metabolic liver disease
• Lymphoma or other lymphoproliferative disorders
• Monoclonal IgA gammopathy, including monoclonal gammopathy of undetermined significance or multiple myeloma

The phrase “high IgA” does not mean that IgA is attacking the body, and it does not prove IgA nephropathy. In IgA nephropathy, abnormal IgA-containing immune complexes deposit in the kidneys, but total serum IgA may be normal or high. Urinalysis, urine protein measurement, kidney function, blood pressure, and sometimes kidney biopsy—not the serum IgA concentration—establish the diagnosis.

The central laboratory distinction is polyclonal versus monoclonal. A broad increase in the gamma region on serum protein electrophoresis favors polyclonal immune activation. A narrow spike or band raises concern for one clone of plasma cells. Immunofixation can then identify whether the abnormal protein is IgA kappa, IgA lambda, or another type. An isolated mild increase with a clear inflammatory or liver explanation is very different from an IgA elevation accompanied by anemia, kidney impairment, high calcium, bone pain, weight loss, or an abnormal free-light-chain ratio.

The height of the value alone rarely identifies the cause. Trend, symptoms, and accompanying results matter more. A stable mild elevation over years may be monitored, while a new rapid rise or monoclonal pattern warrants targeted evaluation.

IgA and Celiac Disease Testing

Total IgA has a special role in celiac disease testing because the standard screening antibody, tissue transglutaminase IgA (tTG-IgA), depends on the patient being able to produce IgA. If total IgA is very low, tTG-IgA and endomysial IgA can be falsely negative even when celiac disease is present.

For most adults and older children who are eating gluten, tTG-IgA plus a total serum IgA measurement is a common first approach. A tTG-IgA test is interpreted differently when total IgA is deficient. In that situation, clinicians generally use IgG-based testing, such as tTG-IgG or deamidated gliadin peptide IgG, and may proceed to specialist assessment or small-bowel biopsy depending on symptoms and results.

A complete celiac disease antibody panel may include total IgA, tTG-IgA, endomysial IgA, and selected IgG-based antibodies. Ordering every antibody is not always necessary, but checking total IgA prevents an important blind spot.

Testing is most accurate while the person is eating gluten. Starting a strict gluten-free diet before blood tests or biopsy can lower antibody levels and allow the intestinal lining to heal, producing a false-negative workup. Anyone already avoiding gluten should discuss a supervised gluten challenge or alternative diagnostic plan with a gastroenterologist rather than restarting large amounts without guidance.

Several result combinations illustrate the logic:

• Normal total IgA and negative tTG-IgA: Celiac disease becomes less likely, although it is not impossible if gluten intake is low, symptoms are compelling, or another technical issue exists.
• Normal total IgA and positive tTG-IgA: Celiac disease is possible; the degree of elevation, endomysial antibody, age, symptoms, and biopsy strategy guide confirmation.
• Low total IgA and negative tTG-IgA: The negative IgA antibody result is unreliable; IgG-based testing is needed.
• Low total IgA and positive tTG-IgG or DGP-IgG: Celiac disease requires further evaluation, usually with gastroenterology input.
• Low IgA without celiac antibodies: The IgA finding still deserves independent interpretation, especially if infections or autoimmune symptoms are present.

Selective IgA deficiency and celiac disease occur together more often than chance alone would predict. Their overlap is clinically important because celiac disease can cause diarrhea, iron deficiency, low bone density, fatigue, weight change, and other findings that might otherwise be attributed to an immune disorder.

Follow-Up Tests and Result Patterns

Follow-up depends on whether IgA is low, high, newly abnormal, persistent, or accompanied by symptoms. A repeat quantitative immunoglobulin panel is often the first step when a result is unexpected or only mildly abnormal. Repeating the test can confirm persistence and show whether IgG or IgM is also changing.

For low IgA, evaluation may include:

• IgG and IgM concentrations
• IgG subclasses when recurrent bacterial respiratory infections are present
• Antibody responses to protein and polysaccharide vaccines
• Complete blood count and lymphocyte subsets
• Review of medicines and immune-suppressing treatments
• Testing for protein loss, kidney disease, or intestinal disease
• Celiac testing with an IgA-aware strategy
• Referral to an allergist or clinical immunologist for recurrent, severe, unusual, or treatment-resistant infections

The pneumococcal antibody titer test assesses functional IgG responses to specific pneumococcal serotypes. It can reveal an antibody-quality problem even when total IgG is normal. Tetanus or diphtheria antibody titers may assess responses to protein vaccines.

For high IgA, common follow-up tests include:

• Complete blood count, metabolic panel, and liver tests
• C-reactive protein or erythrocyte sedimentation rate when inflammation is suspected
• Urinalysis, urine protein-to-creatinine ratio, creatinine, and blood pressure if kidney disease is possible
• Serum protein electrophoresis, immunofixation, and serum free light chains when a monoclonal protein is a concern
• Infection-specific or autoimmune testing chosen from the clinical picture
• Imaging or specialist referral based on organ symptoms rather than the IgA value alone

Patterns are more informative than isolated numbers. Low IgA with normal IgG and IgM suggests selective or partial IgA deficiency. Low IgA plus low IgG suggests a broader antibody deficiency, medication effect, protein loss, or blood-cell disorder. High IgA with high IgG and a broad electrophoresis pattern often reflects polyclonal inflammation. High IgA with a narrow monoclonal band and abnormal kappa/lambda ratio raises concern for a clonal plasma-cell condition.

Results should also be compared with previous values. A stable lifelong low IgA in an otherwise healthy person requires a different response from a rapid decline after immune therapy. Likewise, a chronic mild polyclonal elevation differs from a newly developing monoclonal IgA protein.

Next Steps and When to Seek Care

Start by confirming the units, age-specific reference range, and whether the value was measured alone or as part of a panel. Bring prior results and a complete medication list to the clinician. A useful discussion connects the result to infection frequency, gastrointestinal symptoms, autoimmune history, liver risk factors, kidney findings, and family history.

For a low result, record how often infections occur, whether antibiotics are repeatedly needed, and whether pneumonia, chronic sinus disease, or persistent diarrhea has occurred. Vaccination records help an immunologist decide whether functional antibody testing is appropriate. Do not take unproven “immune-boosting” supplements to raise IgA; no over-the-counter product reliably corrects selective IgA deficiency, and some supplements interfere with medicines or liver tests.

For a high result, the next step is usually to identify whether the elevation is polyclonal or monoclonal and whether another organ system shows abnormalities. Reducing alcohol exposure, managing metabolic risk, or treating an infection may improve a secondary elevation, but the IgA number itself is not usually a treatment target.

Seek prompt medical care for fever with breathing difficulty, confusion, severe weakness, dehydration, rapidly worsening infection, coughing blood, or signs of sepsis. Kidney warning signs such as visible blood in urine, marked swelling, sharply reduced urine output, or very high blood pressure also need urgent assessment. During or soon after a transfusion, hives, wheezing, throat tightness, dizziness, or collapse is an emergency.

Most isolated IgA abnormalities are not emergencies. Careful confirmation, pattern recognition, and symptom-based follow-up usually provide more useful answers than reacting to the number alone.

References

• Diagnosis and Management of Celiac Disease 2023 (Guideline)
• Understanding the natural history of selective IgA deficiency 2025
• Immunoglobulin A (IgA): Function, Tests & Disorders 2025
• Selective IgA Deficiency 2023 (Review)
• Polyclonal hypergammaglobulinaemia: assessment, clinical interpretation, and management 2021 (Review)
• Serum immunoglobulin A levels: Diagnostic utility in alcoholic liver disease and association with liver fibrosis in steatotic liver disease 2024

Disclaimer

This information is educational and does not diagnose the cause of a high or low IgA result. Reference ranges, celiac testing strategies, and follow-up needs vary by age, laboratory, symptoms, and medical history. Discuss abnormal results with a qualified clinician, and seek urgent care for severe infection, breathing problems, kidney warning signs, or a suspected transfusion reaction.