An overdose of magnesium can lead to heart and respiratory problems The demand for dietary supplements with magnesium is increasing by 3% every month. The popularity of the supplement increased thanks to the Internet, where users said that they became calmer after a course of pills. But uncontrolled consumption of magnesium can land you in the hospital. An overdose can lead to diarrhea, headaches, breathing problems and heart rhythm, said endocrinologist, head of the department of clinical disciplines at NMI Anton Ershov.