Magnesium supplements can cause gastrointestinal side effects like nausea, vomiting, diarrhea, and stomach pain. However, these side effects typically occur in doses larger than 350 milligrams.

If you take too much magnesium, you could experience symptoms like diarrhea, muscle weakness, headache, low blood pressure, and facial flushing. Untreated hypermagnesemia (when there's too much ...