What’s the difference between the celiac disease test and the celiac disease monitoring test?
For the "Monitoring" test (for those already diagnosed with celiac), you do not need to be eating gluten. It measures the effectiveness of your gluten-free diet.
For the "Screening test" (to test your likelihood of having celiac), you do need to follow the gluten challenge protocol if you’re already gluten-free. If you’re already eating a reduced gluten or gluten-free diet, then you need to eat, at minimum 2 crackers, a slice of bread, or equivalent for 8 weeks.