an adolescent with chronic giardiasis mimicking anorexia nervosa a 13yearold hispanic female presented with symptoms of abdominal pain amenorrhea and unintentional weight loss of 11 kg preliminary investigation yielded no immediate causes and an initial differential included inflammatory bowel disease ibd celiac disease as well as viral bacterial or parasitic gastrointestinal infection evaluation of these potential diagnoses yielded negative results thus the team thought that the patient may be suffering from anorexia nervosa the patient was discharged to outpatient care and was treated in our adolescent health clinic where repeat laboratory testing yielded a positive giardiaantigen test the patient was placed on metronidazole rapidly gained weight and resumed menstruation soon after the final diagnosis was chronic giardiasis chronic giardiasis is a rare and enigmatic disease that presents with many symptoms similar to chronic gastrointestinal disorders eg ibd and celiac disease and anorexia nervosa practitioners involved in the diagnosis and treatment of anorexia nervosa should be aware of this disorder and include it in differential diagnoses of patients presenting with anorexia nervosa symptoms