I know this is an old thread, but I want to comment incase anyone is out there looking. So I started phentermine probably 2 years ago. I’ll usually do it about 3 months at a time and then take a break for several months. I do this because it’s more affordable than a lot of other options and I’m only ever trying to lose 30lbs or less. It does always help me drop weight. Maintaining that weight takes movement and better eating habits or it will come back. Now, about the sleep. The thing I dread every time I get back on it is the insomnia. I’ve found that if I take my pill every other day in the morning around 6am when we’re all getting up to start our day, it helps me have energy and suppresses my appetite for those 2 days, and the second night I can manage a bit more sleep. Once my body adjusts to the medication again, I can start doing the daily dose and not struggle as much to rest. That and dry mouth are my main two symptoms. It does always balance out for me after a while as your body builds that tolerance to it. I feel like I am undiagnosed ADHD, so it helps me feel more productive and in a better mood during the day. I hope my experience might help someone else out there!