"i started phentermine 37.5 mg on 3/11/2017.  it is not affecting me at all and how i know this is back in 1997--i took &quot;phen-phen&quot; and lost over 30 lbs in a month.  i would get &quot;the feeling&quot; you get and i had bad insomnia.  i am 45 years old and 5&#039;1 and weigh 203.  back in 2014, i weighed in at a whopping 247 and by 2016, i have been hovering right around 203--hence, why i decided to try phentermine again.  i lost the previous weight by counting calories and it did indeed work.  could it be that the phentermine is not working because maybe i need adipex instead?  idk, but it has me really flustered.  i can sleep and eat.  it&#039;s crazy. "