<<Disclaimer: Verify this information before applying it to your situation.>> The literature I have read says that diagnosis can be made very shortly after re-introducing gluten to the diet. If Andy has diarrhea that soon after re-introducing gluten, the GI guy can test for damage to the bowel then. Virginia is two and a half. She has very severe symptoms and becomes very ill in less than a day after accidently ingesting gluten. If Andy has so many problems with it, it would be torture for him to have to go through that for a month! Sarah Rogers