 The level of symptoms may determine the order of the tests, but "all" tests lose their usefulness if the person is already eating a gluten-free diet.Intestinal damage begins to heal within weeks of gluten being removed from the diet, and antibody levels decline over months.For those who have already started on a gluten-free diet, it may be necessary to perform a rechallenge with some gluten-containing food in one meal a day over 6 weeks before repeating the investigations.