An IgA blood test measures immunoglobulin A, the most abundant antibody guarding the moist linings of your gut, airways, and other surfaces that meet the outside world. Because these barriers are where many germs first try to get in, your IgA level offers a useful window into how well your everyday defenses are working.
Doctors order this test for many reasons: recurrent infections, digestive problems, a suspected autoimmune condition, or an unexpected result on another blood panel. On its own, an IgA value rarely delivers a diagnosis, but read alongside your symptoms and other markers it helps point the way.
In this article you will learn what immunoglobulin A does, why the test is ordered, and what high, low, and normal IgA levels can mean, along with the newest thinking on the celiac and kidney conditions linked to this antibody.
What is immunoglobulin A (IgA)?
Immunoglobulin A, or IgA, is one of five antibody types your immune system produces. Antibodies are Y-shaped proteins that recognize germs and other threats and either neutralize them directly or tag them for removal. IgA stands out because it does most of its work at the body’s wet surfaces — the linings of your nose, throat, lungs, and digestive tract — rather than deep inside the blood.
These moist linings, called mucous membranes, are where a huge share of viruses and bacteria first make contact with you. IgA patrols them like a guard at the door, sticking to germs and trapping them in mucus so they can be swept away before they cause trouble. Immunologists call this immune exclusion: keeping invaders out rather than fighting them once they are inside.
Where IgA does its work
You will find IgA in saliva, tears, sweat, breast milk, and the fluids of your gut and airways, as well as in your blood. In breast milk, IgA passed from parent to baby helps protect a newborn’s gut before the baby’s own immune system matures. This broad presence is why a shortage of IgA often shows up as repeated infections of the sinuses, chest, or bowel.
Two forms: circulating and secretory
IgA comes in two main forms. Circulating IgA travels in the bloodstream, and this is what a standard IgA blood test measures. Secretory IgA is a sturdier version released into saliva, tears, and gut fluids, built to survive harsh environments like the digestive tract. A blood draw captures the circulating form, while specialized saliva tests can gauge the secretory form when a clinician needs it.
What an IgA blood test measures and why doctors order it
An IgA blood test reports the amount of immunoglobulin A circulating in your blood, usually in milligrams per deciliter (mg/dL). It is a simple blood draw, often run together with immunoglobulin G (IgG) and immunoglobulin M (IgM) as part of a wider immune workup. The three antibodies each tell a different part of the story, which is why they are frequently measured as a set.
Your care team may order the test for several reasons:
- You get frequent or unusual infections, especially of the sinuses, lungs, or gut.
- You have ongoing digestive symptoms, such as chronic diarrhea, that could point to celiac disease.
- An autoimmune condition is suspected and your doctor wants a fuller immune picture. In that case they may also run an autoimmune panel.
- Another test, such as a total protein measurement, came back unexpectedly high or low and needs explaining.
- You are being checked for a plasma-cell disorder that can overproduce a single antibody.
Fasting is not usually required for an IgA test, although your visit may include other tests that do call for it.
IgA normal range and how to read your results
A typical adult IgA level sits roughly between 60 and 400 mg/dL, but the exact reference range depends on the laboratory, your age, and the testing method. Always read your result against the range printed on your own report rather than a general figure. IgA is naturally low in newborns and rises through childhood into adulthood, so a child’s normal is not the same as an adult’s.
A single IgA number rarely stands alone. Doctors interpret it alongside your IgG and IgM levels, your symptoms, and sometimes a protein test that separates the different antibody families. A value flagged as high or low is a prompt to look closer, not a diagnosis in itself, and everyday factors often explain a small shift.
What high IgA levels can mean
A raised IgA can arise in two very different patterns, and telling them apart matters because they lead to different next steps.
A broad rise (polyclonal)
La mayoría de los resultados con IgA elevada son policlonales, lo que significa que muchas células inmunitarias diferentes están produciendo anticuerpos adicionales al mismo tiempo. Esta es la respuesta normal del cuerpo ante un desafío. Los desencadenantes más comunes incluyen infecciones crónicas o repetidas, inflamación prolongada y enfermedades hepáticas crónicas como la cirrosis, que pueden elevar la IgA. Esa relación con el hígado es una de las razones por las que los médicos suelen pedir también pruebas de función hepática. Varias enfermedades autoinmunes elevan la IgA de la misma manera general.
Un pico marcado (monoclonal)
Con menos frecuencia, la IgA sube porque un solo clon de células plasmáticas se multiplica y produce un único anticuerpo idéntico. Este patrón monoclonal puede indicar mieloma múltiple de tipo IgA o un estado precanceroso conocido como GMSI (gammapatía monoclonal de significado incierto). Un pico monoclonal generalmente se detecta mediante un estudio especializado. Para ver cómo aparece ese pico en un resultado de laboratorio, puedes leer nuestra guía sobre electroforesis de proteínas e inmunoglobulinas.
Qué significan los niveles bajos de IgA y la deficiencia selectiva de IgA
Un nivel de IgA bajo o indetectable es bastante común, y para muchas personas no causa ningún síntoma. La causa más frecuente es la deficiencia selectiva de IgA, en la que el cuerpo produce poca o ninguna IgA mientras que la IgG y la IgM se mantienen normales. Es la inmunodeficiencia primaria más común, y afecta aproximadamente a 1 de cada 300 a 1 de cada 700 personas de ascendencia europea; muchas nunca saben que la tienen.
Otras personas no tienen tanta suerte. Como la IgA protege las membranas mucosas, quienes tienen niveles bajos pueden presentar infecciones recurrentes en los senos paranasales, el pecho y el intestino. La deficiencia selectiva de IgA también está relacionada con una mayor frecuencia de alergias y enfermedades autoinmunes, incluyendo la enfermedad celíaca y la enfermedad inflamatoria intestinal. Dada esa relación con las alergias, algunas personas también leen nuestra guía sobre los estudios de sangre para alergias y la IgE. Un nivel de IgA muy bajo también puede reducir tus globulinas totales en un panel de rutina, y puedes leer nuestro artículo sobre niveles bajos de globulinas.
La nota sobre transfusiones
Un pequeño subgrupo de personas con deficiencia selectiva de IgA produce anticuerpos contra la propia IgA. Si reciben hemoderivados que contienen IgA, pueden tener, en casos raros, una reacción alérgica grave. Por eso vale la pena informar a tu equipo médico sobre una deficiencia de IgA conocida antes de cualquier transfusión o ciertos tratamientos. Es una precaución sensata, no un motivo para alarmarse.
Qué pueden indicar los niveles altos y bajos de IgA
La tabla a continuación resume las asociaciones más comunes. Lee cada fila como una posibilidad a explorar con un médico, no como un diagnóstico.
| Resultado de IgA | Lo que puede indicar |
|---|---|
| IgA alta, elevación amplia (policlonal) | Infecciones crónicas o recurrentes, inflamación prolongada, enfermedad hepática crónica como la cirrosis, y algunas enfermedades autoinmunes |
| IgA alta, pico pronunciado (monoclonal) | Proliferación de un solo clon de células plasmáticas, que se observa en el mieloma múltiple de tipo IgA o en el estado precanceroso GMSI |
| IgA baja o indetectable | Deficiencia selectiva de IgA, una deficiencia más amplia de anticuerpos, o un efecto secundario de ciertos medicamentos |
| IgA normal | Producción de anticuerpos dentro del rango esperado para tu edad; es posible que se necesiten otros estudios si los síntomas persisten |
En qué se diferencia la IgA de la IgG y la IgM
La IgA es más fácil de entender si la comparas con sus dos parientes más estudiados. Cada clase de anticuerpo tiene una función distinta y un lugar diferente en el cuerpo.
| Anticuerpo | Función principal | Dónde se encuentra |
|---|---|---|
| Inmunoglobulina A (IgA) | Protege las superficies mucosas y bloquea los gérmenes antes de que entren al cuerpo | Saliva, lágrimas, leche materna y el recubrimiento del intestino y las vías respiratorias |
| Inmunoglobulina G (IgG) | Proporciona inmunidad duradera y memoria después de una infección o vacunación | El anticuerpo más abundante en la sangre y el líquido tisular |
| Inmunoglobulina M (IgM) | Actúa como primera respuesta ante una infección nueva | Principalmente en sangre y linfa; se produce al inicio y luego cede el paso a la IgG |
Como las tres se relacionan entre sí, los médicos suelen analizarlas en conjunto. Por ejemplo, una IgA baja con IgG e IgM normales apunta hacia una deficiencia selectiva de IgA, mientras que niveles bajos en las tres sugieren un problema más amplio de anticuerpos.
Condiciones relacionadas con la IgA que debes conocer
Enfermedad celíaca y la prueba tTG-IgA
La enfermedad celíaca es una reacción autoinmune al gluten, y la IgA es clave en su diagnóstico. El principal análisis de sangre de tamizaje busca anticuerpos IgA contra la transglutaminasa tisular, conocido como tTG-IgA. Un resultado positivo es una señal importante, aunque un especialista confirma el diagnóstico antes de que cambies tu alimentación. Para entender la enfermedad en sí, puedes consultar nuestra guía sobre la enfermedad celíaca e intolerancia al gluten. Como la prueba depende de la IgA, una deficiencia oculta de IgA puede dar un resultado falsamente normal, que es exactamente por qué los laboratorios revisan tu IgA total al mismo tiempo.
Nefropatía por IgA (enfermedad de Berger)
En la nefropatía por IgA, también llamada enfermedad de Berger, la IgA se acumula en los pequeños filtros de los riñones, llamados glomérulos, y los daña de forma gradual. Con frecuencia se manifiesta como sangre o proteína en la orina, a veces justo después de un resfriado o dolor de garganta. Cuando se sospecha, los médicos suelen analizar la orina y solicitar un panel de función renal. También puedes leer nuestra guía sobre proteína en la orina. Un diagnóstico definitivo generalmente requiere una biopsia renal, ya que el nivel de IgA en sangre por sí solo no puede confirmarlo.
Vasculitis por IgA
IgA vasculitis, previously called Henoch-Schonlein purpura, is a condition in which IgA-containing immune deposits inflame small blood vessels. It causes a raised purple rash, joint aches, tummy pain, and sometimes kidney involvement. It is most common in children and often settles on its own, though it needs monitoring. As with Berger disease, a blood IgA level supports the picture but does not make the diagnosis by itself.
Cuándo consultar a tu médico
An IgA result is a signpost, and the symptoms around it matter most. Consider speaking with a clinician if you notice:
- Frequent or hard-to-shift infections of the sinuses, chest, or gut.
- Ongoing digestive symptoms such as chronic diarrhea, bloating, or unexplained weight loss.
- Blood in the urine, tea-colored urine, or persistently foamy urine that could signal kidney trouble.
- A raised purple rash with joint or abdominal pain, especially in a child.
- A family history of immune deficiency, celiac disease, or kidney disease alongside your own symptoms.
If you already know you have selective IgA deficiency, mention it before any transfusion, keep up with recommended vaccinations, and treat infections promptly.
Latest scientific advances in IgA testing and care
Research on immunoglobulin A has moved quickly in the past few years, especially around celiac disease and the kidney condition linked to IgA. Here is what the newest reviews suggest, in plain language.
Celiac testing leans more on IgA, and sometimes skips the biopsy
The blood test for celiac disease looks for IgA antibodies against a gut enzyme called tissue transglutaminase (tTG-IgA). In 2025 the European Society for the Study of Coeliac Disease updated its guidelines, and a 2026 review in the New England Journal of Medicine reached a similar point: when tTG-IgA is very high, around ten times the upper limit of normal, selected adults may now be diagnosed without a gut biopsy. What this means for you is that some people could avoid an invasive procedure, but this remains a decision a specialist makes, not something to read from a result on your own.
A positive celiac antibody is a strong clue, not a verdict
A large 2025 study in the journal Pediatrics looked at how well a raised tTG-IgA predicts celiac disease. A very high level was correct in the large majority of children, but a mildly raised level was wrong often enough that the authors urged confirmation before any diet change. What this means for you: if your tTG-IgA comes back positive, keep eating gluten until a doctor confirms the diagnosis, because going gluten-free too early can mask the disease and make it harder to confirm.
Why the lab checks your total IgA first
Here is the catch that ties these threads together. If you have selective IgA deficiency, the standard IgA-based celiac test can look falsely normal, simply because you do not make much IgA. A 2023 review of celiac serology confirmed that IgG-based tests work better in this situation. What this means for you: labs now often measure your total IgA at the same time as tTG-IgA, so a hidden deficiency does not lead to a missed diagnosis.
New treatments are changing IgA nephropathy
IgA nephropathy, where IgA builds up in the kidney’s filters, was long managed mainly with blood-pressure medicines. That is changing fast. Two 2025 analyses that pooled many clinical trials found that several newer drug classes, including targeted immune and complement therapies, lower protein in the urine and slow the loss of kidney function. What this means for you: an abnormal IgA or kidney result now opens the door to more treatment options than a few years ago, although some of these drugs are new and their long-term results are still being gathered.
Allergies can occasionally flag an immune difference
A 2025 review of allergic disease noted that stubborn allergies sometimes sit alongside an underlying immune condition, including selective IgA deficiency. What this means for you: when allergies come together with frequent infections, a doctor may look at your immunoglobulin levels to see the fuller picture.
Glossary of IgA terms
| Término | Definición |
|---|---|
| Inmunoglobulina A (IgA) | An antibody that protects the moist linings of the gut, airways, and other surfaces from germs. |
| Anticuerpo | A protein made by the immune system to recognize and neutralize germs. |
| Mucous membranes | The moist linings of the mouth, gut, airways, and other passages that meet the outside world. |
| Selective IgA deficiency | A common immune condition in which the body makes little or no IgA while other antibodies stay normal. |
| Polyclonal increase | A broad rise in antibodies from many immune cells, usually a sign of infection or inflammation. |
| Monoclonal increase | A rise driven by one identical clone of plasma cells, which calls for further testing. |
| Tissue transglutaminase IgA (tTG-IgA) | The main blood test used to screen for celiac disease. |
| Nefropatía por IgA | A kidney condition, also called Berger disease, in which IgA builds up in the kidney’s filters. |
| Secretory IgA | The hardy form of IgA released into saliva, tears, and gut fluids. |
| Plasma cells | White blood cells that produce antibodies. |
Preguntas frecuentes
Do I need to fast before an IgA blood test?
No. An IgA blood test does not require fasting, because food and drink do not meaningfully change your circulating immunoglobulin A. You can eat and drink normally beforehand. The exception is when your appointment bundles other tests that do need fasting, such as glucose or a lipid panel. In that case, follow the strictest instruction on your lab slip. If you are unsure what applies to your visit, you can read our guide to fasting before a blood test or ask the lab when you book.
What is a normal IgA range?
For most adults, a normal IgA level falls roughly between 60 and 400 mg/dL, but every laboratory sets its own reference range using its own equipment. Age matters too: infants make very little IgA, and levels climb through childhood before leveling off in adulthood. Because of this, the only range that truly applies to you is the one printed next to your result. A value slightly outside the range is common and is usually a cue for context, not alarm.
Does a high IgA level always mean something serious?
Not at all. Most high IgA results come from everyday immune activity, such as a lingering infection, ongoing inflammation, or a chronic liver condition. This broad, polyclonal rise is the body doing its job. Less commonly, a sharp, single-antibody spike can point to a plasma-cell disorder that needs follow-up. Your doctor tells the two apart with further testing, often a protein electrophoresis. A high number on its own is a reason to investigate, not a diagnosis, so try not to read too much into one value.
Can low IgA or selective IgA deficiency be treated?
There is no treatment that makes the body produce more IgA, and most people with selective IgA deficiency need no treatment at all. Care focuses on the symptoms: treating infections promptly, staying up to date on vaccines, and managing any linked conditions such as allergies, celiac disease, or autoimmune problems. Standard antibody replacement therapy does not replace IgA and is not used for isolated IgA deficiency. If infections are frequent or severe, an immunologist can help build a plan tailored to you.
Why does the lab measure total IgA before a celiac test?
The main celiac screening test looks for IgA antibodies against tissue transglutaminase (tTG-IgA). If you happen to have low or absent IgA, that test can read falsely normal even when celiac disease is present, simply because you do not make enough IgA to register. Measuring your total IgA at the same time flags this situation, so the lab can switch to IgG-based celiac tests when needed. It is a safeguard that helps avoid a missed diagnosis in people with selective IgA deficiency.
Can children have an IgA test, and are the numbers different?
Yes, children can have an IgA blood test, and their expected values differ from adults. Babies are born with very little IgA of their own and rely on antibodies from breast milk early on. IgA then rises gradually throughout childhood, so pediatric labs use age-based reference ranges. A low IgA in a young child is not automatically a concern, because levels may simply catch up with time. A pediatrician interprets the result against the child’s age and overall health.
Fuentes
- MedlinePlus, National Library of Medicine — Immunoglobulins (IgA, IgG, IgM) Blood Test — medlineplus.gov
- Cleveland Clinic — Immunoglobulin A (IgA): Function, Tests and Disorders — my.clevelandclinic.org
- Mayo Clinic — IgA nephropathy (Berger disease), Symptoms and causes — mayoclinic.org
- Al-Toma A, Zingone F, Branchi F, et al. — European Society for the Study of Coeliac Disease 2025 updated guidelines on the diagnosis and management of coeliac disease in adults, Part 1 — United European Gastroenterology Journal, 2025 — doi.org/10.1002/ueg2.70119
- Murray JA, Husby S — Celiac Disease — New England Journal of Medicine, 2026 — doi.org/10.1056/NEJMcp2415548
- Chang D, Wong M, Cardenas MC, et al. — Positive Predictive Value of Tissue Transglutaminase IgA for Celiac Disease — Pediatrics, 2025 — doi.org/10.1542/peds.2025-070897
- Volta U, Bai JC, De Giorgio R — El papel de la serología en el diagnóstico de la enfermedad celíaca — Gastroenterology and Hepatology from Bed to Bench, 2023 — doi.org/10.22037/ghfbb.v16i2.2713
- Kim D, Neuen BL, Perkovic V, Wong MG — Efectos de las terapias sobre la proteinuria y la TFGe en la nefropatía por IgA: metaanálisis de ensayos aleatorizados — Clinical Journal of the American Society of Nephrology, 2025 — doi.org/10.2215/CJN.0000000839
- Chen B, Zhu Y, Yang Y, Xu G — Eficacia y seguridad de los tratamientos para la nefropatía por IgA: un metaanálisis en red de ensayos clínicos aleatorizados y controlados — Frontiers in Medicine, 2025 — doi.org/10.3389/fmed.2025.1515723
- Alska E, Doligalska A, Napiorkowska-Baran K, et al. — Carga global de las alergias: mecanismos de desarrollo, retos en el diagnóstico y tratamiento — Life (Basel), 2025 — doi.org/10.3390/life15060878
Lecturas recomendadas
- Cómo leer tus resultados de análisis de sangre
- Valores normales en estudios de laboratorio
- Resultados anormales en estudios de laboratorio
- Biometría hemática (BH)
- Prueba de serología explicada
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