There have been cases where a doctor will prescribe 2 doses of the
37.5 phentermine a day, or combining the 37.5's together with a lower dose too-but I wouldn't do that without being under close supervision of a dr.
I think that the people who get those huge doses are either extremely overweight and require that to get the effects due to sheer body mass (like alot of different meds-being bigger means you need more medication to have the same effect a smaller person does)-or for people who have been on it for a long time and the doctor has noted a severe tolerance.
It wouldn't be wise to make that decision on your own. The possible side effects from taking phentermine, like the heart palpitations and higher blood pressure, would literally be doubled and could cause something unexpected and dangerous.
I've said it before, and I'll say it again. Phentermine is designed to help us not to OVEReat-not to not ever want any food. Just because you feel hungry does not mean it's not working. It also cannot do ANYTHING about emotional eating-like what we do when we're bored, angry, sad, or lonely.
Phentermine mimics the effects of adrenaline (the fight or flight chemical) in the brain, which in a roundabout way blocks the hunger signal and gives a false feeling of fullness by keeping those receptors busy. That doesn't mean that we have a bad day we won't ever want to console ourselves with a bowl of ice cream, because those types of cravings are completely separate from the "hunger circuit".
If you are still able to lose weight and don't have the desire to overeat, then it's still working. Medically speaking, the protocol for phen states that if you lose atleast 4 pounds in a month, then it's still considered to be effective. Doesn't sound like much, I know-but we all tend to be our own worst critics and skeptics...