"day one on this medication....had taken phentermine before, gotten to goal weight, then thought i could maintain on my own, with exercise etc. had some winter weight gain and getting started again. my doctor asked if i wanted to try something new. at first made me a little light headed, but better as the day went on. problem is now, i have to be up in a couple of hours and can&#039;t go to sleep!..hoping this goes away soon. tomorrow will take it a little earlier in the day."