Purpose Anorexia nervosa (AN) is a psychiatric disorder which can lead to numerous medical complications. In the clinical practice, during weight restoration, it is relatively common to observe potentially fatal complications, such as refeeding syndrome (RS). The objective of this case report is to highlight some key factors regarding nutritional support and the therapeutic approach in AN to avoid life-threatening complications, for example severe hypophosphatemia. Methods We present the case of a 14-year-old girl suffering from AN, who was admitted to our hospital with lethargy, emaciation with bitemporal wasting, hirsutism and pitting lower extremity edema. Results Based on the laboratory findings, the concerning condition of the patient was attributed to hypophosphatemia (1,64 mg/dl) caused by RS. Conclusions Refeeding syndrome is a potentially lethal condition in the case of AN patients. Hypophosphatemia, which is a result of the refeeding syndrome, is a relatively common complication of overly aggressive nutritional rehabilitation. Physicians who are involved in treating this condition, should be aware of this potentially life-threatening syndrome, and assess their therapeutic approach accordingly Keywords: anorexia nervosa, hypophosphatemia, refeeding syndrome, nutritional support,