It makes the body react against the substances in it. Actually drugs that are produced by the medical profession have tons of complications, and the sole way you can avoid them is to get a doctor to pen you a prescription. The complications of phentermine are like those you get when you are undergoing stress. You must enhance your diet and boost your health simultaneously you are losing pounds. Follow the prescription and directions your GP gives you. Discover more on Lose Weight. Additionally, don't take larger doses than you are told to, as this could only increase possible side-effects. What Are The Probable Complications? Insomnia , irritation, dry mouth, hard stools or belly upset might be experienced in the 1st a few days while your body is adjusting to Phentermine. Why is phentermine just utilised for one or two weeks? This is because of the fact that it's all you want to shed the pounds. You just have to control yourself with how much food that you eat, and will yourself to exercise.