Anorexia nervosa and bulimia are emotional disorders which are a serious hazard to the physical health or life. They most often affect girls and young women and disorganize their mental and social life. In this paper, complications caused by eating disorders as a result of deficiency or excessive loss of bioelements by an organism are reviewed along their influence on the quality of life. The symptoms of anorexia nervosa are the following: weight loss over 15% of the standard body mass for the age and height, severe fear of body weight gain despite clear evidence of weight deficiency. The main symptoms of bulimia involve uncontrolled overeating and counteracting weight gain which could occur after overeating episodes by self-induced vomitting or overuse of laxatives and diuretics. Medical complications of bulimia are related to the method and frequency of purgation, while in anorexia they are caused by starvation and weight loss. The following deviations are observed in both restrictive and bulimic forms on anorexia: hypokalemia, hypocalcemia, hypophosphatemia and sometimes also hyponatremia, hypomegnesemia and hypochloremic alkalosis. Many electrolytic and acid abnormalities are found in bulimia depending on the method for laxation (self-induced vomitting, misuse of laxatives or diuretics). Most patients adapt well for a relatively long time to low levels of potassium in plasma but sometimes the situation may cause life threatening consequences, like dysrhythmia, paralytic ileus, neuropathy, muscle weakness and paresis. Physicians and patients should understand that anorexia nervosa is a systemic disease and can affect all body organs. Full knowledge about possible complications of anorexia nervosa allows physicians to achieve precise assessment and conduct appropriate treatment of patients when the diagnosis has already been made.