as with anything else, you have to taper down, and only take it during a heavy cycle that keeps you from sleeping otherwise. if your on the juice pretty much year round, I would find something else (l tryptophan, mellatonin or the other suggestions on this thread) also, if you get addicted to shit easily, find something else. otherwise, there's nothing wrong with taking a second 5mg dose if you really can't fall back to sleep. all this stuff affects everyone differently, if you wake up groggy, just go back to sleep, but 10 mg isn't gonna kill anyone. (maybe happy gilmore's grandma). hope this helps.