"i have been on phentermine for a month and have lost 13 lb from 222 to 208. the only side effect is the dry mouth.  since i don&#039;t crave food it&#039;s easy to stick to a low calorie diet. i didn&#039;t get the boost of energy that i wanted on the contrary i felt a little fatigue the doctor said its my body getting used to the low carb diet and the increase of exercise so he gave me a b 12 shot. we will see how month two goes . side note i have been on my weight loss journey for a year i hit a plateau and i am using phentermine as an aid not a quick fix. original weight:256"