I was on Phentermine for approx. 3 months back in 2003. I lost probably 20 lbs in those months, but I was also eating a 1000 cal diet per day. It really screwed my metabolism up, so when I went off of them and started eating "normally", mind you fruits and veggies, lean meats etc. the weight started piling on again. So here we are, 5 years later and 35 lbs. heavier than when I even started taking the pill. It did make me very jittery at first and I was constantly thirsty all of the time. If I took the pills after 1:00 in the afternoon, I would be up half the night. Sometimes I want to go back on them just to make me feel like I'm accomplishing something, but I know that it would be a short term solution and I would probably wind back up in the same situation again. I just really want the weight gone!