Xenical blocks absorption of dietary fat into the bloodstream, thereby reducing the number of calories you get from a meal. At the usual dosage level, it cuts fat absorption by almost one-third. Combined with a low-calorie diet, it is used to promote weight loss and discourage the return of unwanted pounds.

The drug is prescribed for the frankly obese and for merely overweight people who have other health problems such as high blood pressure, diabetes, or high cholesterol levels. Your weight status is determined by your body mass index (BMI), a comparison of height to weight.

Along with dietary fat, Xenical decreases the absorption of some fat-soluble vitamins and beta-carotene. To compensate, you should take a multivitamin containing vitamins A, E, D, and K once a day, at least 2 hours before or 2 hours after taking Xenical.