Why can i only lose 10 lbs while on phetermine? i've been taking it for months and can't lose more than that.

Weight loss: Weight loss is related to calories in and calories used. It is still possible to over eat despite medications (or even gastric bypass). It is more important to eat in a healthy manner and be consistent with activity to achieve a healthy weight. Body mass index may be a better way to evaluate your status than pounds on a scale.

Consider switching: Phentermine, fda-approved for 3 months of continuous use, is an anorexiant, which means it suppresses appetite. It doesn't, in and of itself, cause weight loss. The way to reliably lose weight and keep it off is to eat less (have you been cataloging your calories and nutrition?) or burn more calories (most safely with regular exercise). Try 3 weeks of food log and see if this helps.