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Immunoglobulin A (IgA)

Immunology & Autoimmune

IgAImmunoglobulin ATotal IgA

Review status

Currently under review

Pending specialist review and validation.

What it shows

IgA is a type of antibody your immune system makes to help protect the moist surfaces of your body, such as the nose, throat, lungs, and digestive tract. It is found in blood and in secretions like saliva and tears, and helps your body recognize and respond to germs.

An IgA test measures how much of this antibody is present in your blood. It is often ordered along with other immunoglobulins to evaluate overall immune function, to check for selective IgA deficiency, and to help interpret certain tests for conditions that involve the immune system, such as celiac disease.

Why it matters

Results can point to different health issues. Lower-than-expected IgA can be linked to recurrent sinus or lung infections, certain autoimmune conditions, or problems with protein loss from the gut or kidneys. Some medicines that affect the immune system can also reduce IgA.

Higher-than-expected IgA may occur with chronic inflammation, liver disease, some kidney conditions, or disorders of plasma cells. Your clinician may order IgA together with IgG and IgM, and sometimes with protein electrophoresis, to get a more complete picture.

Understanding your results

Your clinician will interpret your IgA level in the context of your age, symptoms, and medical history. If it is lower than expected, they may confirm the result, look at other immunoglobulins, and review vaccine responses or infection history to see how your immune system is functioning. Many people with selective IgA deficiency feel well, but some need advice on infection prevention and targeted vaccinations.

If your level is higher than expected, your clinician may assess for inflammation, review liver and kidney tests, and consider additional studies, such as electrophoresis, to look for patterns in antibody production. Sometimes elevations are temporary and related to recent illness.

If you are being tested for celiac disease, your total IgA level helps determine which antibody tests are most reliable. When IgA is very low, your clinician may use IgG-based tests instead and may consider follow-up testing based on your symptoms.

Reference ranges

0 – 0.07 g/L

All sexes

0 days – 1 month

0 – 39.99 mg/L

All sexes

0 days – 150 years

0 – 19.99 RU/mL

All sexes

0 days – 150 years

0.03 – 0.17 g/L

All sexes

1 month – 2 months

0.07 – 0.46 g/L

All sexes

2 months – 3 months

0.11 – 0.59 g/L

All sexes

3 months – 4 months

0.13 – 0.7 g/L

All sexes

4 months – 5 months

0.13 – 0.73 g/L

All sexes

5 months – 6 months

0.14 – 0.79 g/L

All sexes

6 months – 7 months

0.14 – 0.87 g/L

All sexes

7 months – 8 months

0.16 – 0.91 g/L

All sexes

8 months – 9 months

0.16 – 1 g/L

All sexes

9 months – 10 months

0.17 – 1.05 g/L

All sexes

10 months – 11 months

0.19 – 1.14 g/L

All sexes

11 months – 1 year

0.21 – 1.31 g/L

All sexes

1 year – 2 years

0.28 – 1.39 g/L

All sexes

2 years – 3 years

0.33 – 1.95 g/L

All sexes

3 years – 4 years

0.38 – 2.39 g/L

All sexes

4 years – 5 years

0.49 – 2.72 g/L

All sexes

5 years – 6 years

0.54 – 3.05 g/L

All sexes

6 years – 7 years

0.57 – 3.26 g/L

All sexes

7 years – 8 years

0.63 – 3.49 g/L

All sexes

8 years – 9 years

0.7 – 3.69 g/L

All sexes

9 years – 10 years

0.76 – 3.93 g/L

All sexes

10 years – 11 years

0.79 – 4.13 g/L

All sexes

11 years – 12 years

0.81 – 4.36 g/L

All sexes

12 years – 13 years

0.82 – 4.57 g/L

All sexes

13 years – 14 years

0.86 – 4.8 g/L

All sexes

14 years – 15 years

0.87 – 5 g/L

All sexes

15 years – 16 years

0.94 – 4.67 g/L

All sexes

16 years – 18 years

0.8 – 4 g/L

All sexes

18 years – 150 years

Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.

Factors that could impact Immunoglobulin A (IgA)

Recent infection or inflammation
Active or recent infections and chronic inflammatory conditions can increase IgA production and may temporarily raise measured levels.
Age and development
IgA production matures over childhood, so expected values differ by age. Labs use age-specific reference ranges to interpret results.
Protein loss or nutrition
Conditions that cause protein loss through the kidneys or intestines, or poor nutrition, can lower circulating IgA concentrations.
Medications and biologics
Corticosteroids, chemotherapy, anti-CD20 therapies like rituximab, and other immunosuppressants can reduce IgA. Recent IVIG can transiently raise measured immunoglobulins.
Liver disease and alcohol use
Chronic liver disease and heavy alcohol use are associated with higher IgA levels, which may influence interpretation.
Sample and timing issues
Severe hemolysis or lipemia may interfere with some assays, and timing relative to infusions or acute illness can affect results.

2026

References

McGill University Health Centre. (2015, October 29). IgA (Task CD 4454104). Laboratory reference ranges.
McGill University Health Centre. (2016, October 20). IgA (Task CD 691222). Laboratory reference ranges.
McGill University Health Centre. (2020, November 23). IgA (Task CD 699341). Laboratory reference ranges.
Bonilla, F. A., Khan, D. A., Ballas, Z. K., Chinen, J., Frank, M. M., Hsu, J. T., Keller, M., Kobrynski, L., Komarow, H. D., Mazer, B., Nelson, R. P., Orange, J. S., Routes, J. M., Shearer, W. T., & Shapiro, R. (2015). Practice parameter for the diagnosis and management of primary immunodeficiency. Journal of Allergy and Clinical Immunology, 136(5), 1186-1205. External link
Rubio-Tapia, A., Hill, I. D., Kelly, C. P., Calderwood, A. H., & Murray, J. A. (2013). ACG clinical guidelines: Diagnosis and management of celiac disease. American Journal of Gastroenterology, 108(5), 656-676. External link