Fluid and magnesium abnormalities are common in patients with high-output stomas. Subcutaneous magnesium administration may be more feasible for long-term management in ambulatory patients, but magnesium sulfate is approved only for intravenous or intramuscular injection. We describe the management of chronic hypomagnesemia and dehydration secondary to a high-output ileostomy following radiation and chemotherapy for anal squamous cell carcinoma with intermittent home-based subcutaneous magnesium infusions in a 61-year-old female with a history of Crohn's disease and multiple bowel resections. Despite aggressive management with intravenous magnesium sulfate and oral magnesium glucoheptonate over 8 months, 49% of her magnesium concentrations were <0.60 mmol/L (mean 0.61 ± 0.09) necessitating 4 emergency, 1 hospital, and 4 infusion clinic visits. After initiation of subcutaneous magnesium sulfate, all magnesium concentrations were >0.60 mmol/L (mean 0.79 ± 0.08 mmol/L over 9 months). The patient tolerated the infusions well, only developing one minor episode of infusion-related cellulitis. A systematic review of the literature identified 14 reports where subcutaneous magnesium sulfate<sub></sub>was effective and treatment for adults or children with hypomagnesemia was safe. Home-based intermittent administration of subcutaneous magnesium may be a helpful and safe intervention to temporarily prevent and treat select patients with recurrent symptomatic hypomagnesemia.