In theory then once your body is used to it that will take a while to kick in. I don't remember how long and I was switching from regular to XR when I started XR so it wouldn't be the same anyway but XR does usually work on a delay, but in the beginning Seroquel is really sedating no matter what for most people. For me XR evens things out and there is a lot less daytime sleepiness than there was on immediate release. In the hospital with immediate release I needed to nap after breakfast until the 10:30 group to be able to function and I fell asleep within an hour of taking it. Which was really nice; usually I don't sleep well IP. But for life outside of the hospital XR is better for me.