Anorexia nervosa is a disorder that is characterized by excessive preoccupation with body weight and shape, and conscious attempts to stay in low weight due to fear of weight gain. Vomiting, one of the methods used by anorexia nervosa patients to stay in low weight, is one of the most important causes of hypokalemia. Diuretics and diarrhea are other common causes of hypokalemia. If hypokalemia is chronic and resistant to treatment, eating disorders and other metabolic conditions should be investigated. One of the rare causes of hypokalemia, an electrolyte imbalance that can cause fatal outcomes, is Gitelman syndrome. Gitelman Syndrome is a genetically inherited disease of the distal tubules which causes hypokalemia, metabolic alkalosis, hypocalcemia, hypomagnesemia and vomiting. It is a syndrome usually diagnosed during adolescence, however it sometimes remains asymptomatic throughout life. Severe symptoms such as tetanus, rhabdomyolysis, and paralysis can also be seen. A case of Gitelman syndrome which was diagnosed as anorexia nervosa due to physical appearance of the patient, low body mass index (BMI), and frequent vomiting and in which the other medical pathologies have not been adequately investigated is presented in this article. Assessments to exclude the medical conditions that may be associated with symptoms are necessary before a diagnosis of a psychiatric disorder is made.