I have been on and off Zyprexa (olanzapine) for a couple of years, most recently for 7 months and counting. The first time I went on it I gained 25 lbs. in about four weeks; this time it's taken me a lot longer, and I haven't gained as much weight. It really helps me keep my head together, and I haven't had any major side effects, even though I'm diabetic and have to watch my blood sugar to make sure the med isn't causing it to go up. So far, so good.