Introduction: Anorexia nervosa is a commonly encountered cause of severe underweight in pediatric settings. It is an eating disorder characterized by the inability to maintain a minimally normal weight, a devastating fear of weight gain, relentless dietary habits that prevent weight gain, and a disturbance in the way in which the body image is perceived. Hypernatremia is an unusual electrolyte imbalance in anorexia nervosa.
Case Report: This is a case of a 12-year-old male admitted with progressive weight loss following restrictive food intake for the preceding one year. He presented with severe hypernatremia. Correction of severe hypernatremia was successful after four to five days. This correction was slow but gradually achieved. There was no altered sensorium throughout admission which remains the worst nightmare of any managing team. Feeding protocol as per Junior MARSIPAN guidelines was adhered to. He made an excellent recovery and was discharged after 24 days of admission with a weight gain of 6.1 kg.
Conclusion: Anorexia nervosa is commonly encountered in pediatric settings and can cause potentially life-threatening physical and psychological complications. Hypernatremia is an uncommon metabolic abnormality; slow correction averts untoward side effects.

Keywords: Anorexia nervosa, Hypernatremia, MARSIPAN guidelines