I take 40mg xr adderall. I started at 15mg, moved to 30mg when it didnt work. Ive taken 30mg for a year now and was just bumped up to 40mg. Its worked better than the 30mg for the past month but the last three days it has been kicking in 2 to 2 1/2 hour after i take it. I've tried taking it with food and without food on an empty stomach. They both have the same outcome. Any idea as to why this just started happening? or how to fix it? I have not changed anything in my diet.