We describe a 14-year-old male who was followed for several years for the diagnoses of avoidant restrictive food intake disorder and generalized anxiety disorder before being diagnosed with primary adrenal insufficiency (PAI) or Addison disease. The patient presented multiple times to different facilities with worsening symptoms of anorexia, nausea, vomiting, and anxiety in the months leading up to diagnosis of PAI. Dehydration and hypotension, occurring relatively late in the course of his illness, were attributed to poor intake and vomiting. Hyponatremia was attributed to his psychotropic medication, olanzapine, and to dehydration. During his third hospitalization, he was diagnosed with PAI; treatment with stress-dose glucocorticoid therapy resulted in rapid clinical improvement. This case serves as a reminder that adrenal insufficiency must be considered in the differential diagnosis of eating disorders because signs and symptoms of adrenal insufficiency can overlap and progress insidiously. Additionally, we recognize that the diagnostic process is intertwined with a patient's medical history and use this opportunity to discuss cognitive, specifically anchoring, bias in academic medicine.