Sympathomimetic appetite suppressants are used in the short-term treatment of obesity. Their appetite-reducing effect tends to decrease after a few weeks. Because of this, these medicines are useful only during the first few weeks of a weight-loss program. The sympathomimetic appetite suppressants can help you to lose weight while you are learning new ways to eat and to exercise. Changes in eating habits and activity level must be developed and continued long-term in order for you to continue losing weight and to keep the lost weight from returning.

In order to prevent trouble in sleeping, if you are taking:
One dose of phentermine a day, take it about 10 to 14 hours before bedtime.
More than one dose of this medicine a day, take the last dose of the day about 4 to 6 hours before bedtime.

For patients taking a long-acting form of phentermine:
Swallow these capsules or tablets whole. Do not break, crush, or chew before swallowing

Take phentermine only as directed by your doctor . Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. If too much is taken, it may cause unwanted effects or become habit-forming.

If you think phentermine is not working properly after you have taken it for a few weeks, do not increase the dose . Instead, check with your doctor.