We report the case of a patient with recurrent severe hypocalcemia, secondary to hypomagnesaemia, and prerenal renal failure, due to ileostomy losses after a colectomy, who needed several admissions to the hospital through more than one year. Finally, he was successfully treated by self-administered subcutaneous magnesium: he reached and maintained normal levels of serum calcium, magnesium and PTH, no more hospital admission were needed and he resumed a normal life.