Celiac Blood Test in Celiac Disease Pre-Diagnosis, Testing & Symptoms Posted March 1, 2008 · Report to Admin After being ill for months on end and getting no help what so ever from my doctors, I decided to try gluten free. I've been on a gluten-free diet for about 6-8 weeks now and have been feeling much better. When I went to my doctor yesterday she said that she wanted to test for Celiac via blood tests. I know that I could get a false negative from having done this, so I asked her how much gluten I would have to consume and for how long I would have to do it for. She basically just said that I shouldn't have "taken it upon myself to do that" and that there are so many things with gluten in them that I probably wasn't doing it right anyway. So.... I never did get my answer. I had seen some posts on here talking about going back to gluten for MONTHS before having the internal tests, but what about the blood tests? How much gluten would it take to trigger the immune response that can be seen via the bloodwork? I heard somewhere else to eat it for about 3 days, but I want to be sure. Thanks!