Background <p>Magnesium toxicity occurs mostly in patients with decreased renal function or in preeclamptic patients who underwent high-dose magnesium sulfate therapy. Iatrogenic injection of magnesium sulfate is a rare condition. Magnesium sulfate extensively influences heart, lung, and brain function. Therefore, it is crucial to manage magnesium sulfate overdose through intensive procedures if common treatments do not improve the patient’s prognosis. Our paper focuses on a case study of a patient who overdosed on magnesium sulfate and was managed through hemodialysis.</p> Case presentation <p>A 50-year-old Iranian woman was admitted to the hospital, following the injection of two vials of magnesium sulfate (25&#xa0;g each) by emergency medicine services mistakenly, instead of the vial of glucose. At the entrance of the emergency ward, she became pulseless, and they initiated cardiopulmonary resuscitation and intubation. Electrocardiogram and laboratory results showed hypermagnesemia. Primary supportive interventions—fluid therapy and calcium gluconate injections—were ineffective in halting the progression of the patient’s symptoms. Therefore, we decided to initiate hemodialysis, which significantly improved the patient’s symptoms. Consequently, she improved and was discharged from the intensive care unit and the hospital.</p> Conclusion <p>Hypermagnesemia is a life-threatening and emergency condition that must be recognized and managed immediately. Hemodialysis should be considered promptly if basic supportive interventions such as calcium gluconate and fluid therapy are ineffective in treating hypermagnesemia.</p>