It worked really fast for my husband. Within a day or two. It worked really well really fast, and then after that is when it started to work less well as time went on. He said after that initial boost he always felt he was "chasing the feeling" he had right at the start.

He was on 10 mg once a day when it worked really well. Later he went up to 20mg once a day, but never wanted to go higher.

The first time he was on it he lost 25 lbs, but not the second time (first time was 3 years ago, second time was just last fall.)