Eating disorders are associated with several medical complications. Growth retardation and osteoporosis can cause permanent sequelae if treatment is delayed. Severe eating disorders are associated with significant mortality. Cardiac arrhythmias are the most common somatic cause of death. Hypokalaemia is a common complication and is associated with increased risk of cardiac arrhythmias. Occasionally, overzealous refeeding may induce a potentially life-threatening condition, the refeeding syndrome. In any patient with severe eating disorder, a physician should perform diagnostic evaluation including assessment of possible somatic complications. This is necessary in order to determine where and how the patient should be treated. Most of the somatic complications of eating disorders are partly or completely reversible if the patient receives adequate treatment in time.