How long does it take to start feeling better after going completely gluten free if you have celiacs disease?

At least a month: Transitioning to being gluten free may take some time. The first few days, even weeks, you may feel pretty lousy. Even worse than before. For most people, but the end of the first month of being gluten free, symptoms are noticeable better. I would also suggest cutting sugar and other grains too if symptoms have not improved much.