t-Transglutaminase (tTG) IgA

This blood test checks for an antibody your immune system makes when it reacts to gluten, and a positive result is a strong signal that celiac disease may be present. If you have already been diagnosed with celiac disease, this test helps your doctor see whether your gluten-free diet is working.

When elevated: Elevated tTG-IgA, particularly at levels ≥10× the upper limit of normal, is strongly associated with celiac disease and significant small intestinal villous atrophy (Marsh 3 lesions). Persistently elevated levels in a diagnosed patient on a gluten-free diet suggest ongoing gluten exposure, dietary non-adherence, or refractory celiac disease, and warrant further clinical evaluation. Untreated or poorly controlled celiac disease is associated with increased risk of malabsorption, nutritional deficiencies, osteoporosis, and small bowel lymphoma. When low: A low or undetectable tTG-IgA in an IgA-sufficient individual on a gluten-containing diet makes active celiac disease unlikely, though it does not entirely exclude seronegative celiac disease, which occurs in a small minority of biopsy-confirmed cases. In a patient with known celiac disease on a gluten-free diet, normalization of tTG-IgA is a favorable indicator of mucosal recovery and dietary adherence. Very low or absent levels have no independent adverse clinical significance beyond their diagnostic context.

tTG-IgA is not athlete-specific but relevant to active individuals if celiac disease is suspected. Undiagnosed celiac disease can impair nutrient absorption (iron, B12, folate), reduce energy availability, delay recovery, and increase injury risk; screening may help explain persistent fatigue, GI distress during training, or performance plateaus.