Persons with weight issues often resort to taking diet pills in their effort to lose weight. However, there are diet pill side effects that one must be careful about. Insomnia, headaches, dry mouth, rapid heart beat, and diarrhea are some of the less serious side effects. However, there are pills which contain strong and/or dangerous ingredients that can wreck havoc to a person's nervous system or may cause cardiac arrest. If you are planning to take diet pills, you should be very careful about what you are taking. Know carefully what the ingredients are, the precautions and the contraindications.