Why isn't the phentermine working this time?

I am wondering The same thing! I took it about 2.5 years ago and lost 12 lbs the first month, total weight loss of about 47 lbs. I have been taking it again and haven't lost anything in months ! The only difference this time is I no longer smoke cigarettes. I really need to figure something out.

The same thing is happening to me Do not know the answer unless we have built up a tolerance My endoc will not let me up my dosage said for me to stop taking it since it is not working I wonder if brand name works better than generic? Does anybody have an answer to that?

I am having a similar issue with Phentermine. I took it two years ago and lost 30 pounds. I gained the weight back plus more. I started back on Phentermine a month ago and while my appetite is suppressed I do not have the extra energy. I read on another forum that all Phentermine is not the same. Some are stronger than others. I asked my pharmacist and was told they had changed distributors so I am thinking it is very possible. The pill I am getting at the Walmart Pharmacy is imprinted K 25, which according to the forum (I cannot find again) is the weakest one.