"i have been on phentermine for 3 days.  i have increased energy and a mild case of dry mouth. i do feel &quot;spacey&quot; at times, but not so much that i cannot drive or work. i am working out harder and drink more water.  i no longer feel hungry and i have control over my sugar addiction.  it took me 3 weeks to lose 12 pounds before i started phentermine.  i have lost 5 pounds in the past 3 days.  tonight is the first night i have not exercised, while on this medication.  it is 1:15 am and i cannot sleep.  will i stop taking this drug?  no!  i will be sure to exercise every night, to aide with sleep."