tTG IgA optimal range and reference range
Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026
Sera's bands for tTG IgA:
- Optimal 0 – 4 U/mL; sufficient 4 – 10 U/mL; out of range below 0 or above 10 U/mL.
Evidence grade: Published reference interval. A band that primarily reflects a published adult laboratory or population reference interval. It is not necessarily applicable to every assay or laboratory.
All units
| Unit | Optimal | Sufficient | Out of range |
|---|---|---|---|
| U/mL | 0 – 4 | 4 – 10 | below 0 or above 10 |
What the evidence says
Two things invalidate this result rather than change it: a low total IgA, which makes a negative meaningless, and a gluten-free diet already underway, which lowers the antibody in someone with untreated disease. The bands follow the Mayo Clinic Laboratories reference values: below 4 U/mL negative, 4 to 10 weak positive, above 10 positive. A result in the 4 to 10 band is a weak positive or equivocal result to follow up, not a reassuring one. Negative cut-offs vary between assays (some call anything below 7 U/mL negative), so the cut-off printed on the report takes precedence; guidelines express their thresholds as multiples of the assay's upper limit of normal for the same reason.
Assay: Results differ meaningfully between platforms and methods. Compare against the interval printed by the issuing laboratory before acting on a borderline value.
Sources
- Tissue Transglutaminase Antibody, IgA, Serum — Mayo Clinic Laboratories, 2026 · Laboratory / reference-interval sourceBelow 4.0 U/mL is negative, 4.0 to 10.0 U/mL weak positive, above 10.0 U/mL positive, at all ages. These are Sera's optimal upper edge of 4 and sufficient upper edge of 10.
- Tissue Transglutaminase (tTG), IgA — Labcorp, 2026 · Laboratory / reference-interval sourceLabcorp's page carries two schemes: 0 to 3 negative, 4 to 10 weak positive, above 10 positive; and below 7.0 negative, 7.0 to 10.0 equivocal, above 10.0 positive. Both end at 10 U/mL, but the negative cut-off differs with the assay.
- European Society Paediatric Gastroenterology, Hepatology and Nutrition Guidelines for Diagnosing Coeliac Disease 2020 — Husby S, Koletzko S, Korponay-Szabó I, et al. — Journal of Pediatric Gastroenterology and Nutrition, 2020 · Clinical guidelineA paediatric guideline, cited only for how thresholds are expressed: as a multiple of the assay's upper limit of normal (10 times) rather than a fixed U/mL figure, and total IgA must be measured alongside.
- American College of Gastroenterology Guidelines Update: Diagnosis and Management of Celiac Disease — Rubio-Tapia A, Hill ID, Semrad C, et al. — American Journal of Gastroenterology (American College of Gastroenterology), 2023 · Clinical guidelineEstablishes tTG IgA as the first-line serologic test, requires total IgA to be measured alongside it because selective IgA deficiency invalidates a negative result, and requires the patient to be eating gluten. It does not set a numeric cut-off — that belongs to the assay.
What tTG IgA (Tissue Transglutaminase IgA) measures
The primary blood screen for coeliac disease, measuring IgA antibodies against tissue transglutaminase.
Only interpretable when total IgA is normal — selective IgA deficiency, which is several times more common in coeliac disease, makes this test falsely negative. The result also depends on gluten still being eaten: a person already gluten-free can test negative with untreated disease.