Comments in this section are limited to effects from taking oral magnesium. Side effects from intravenous use of magnesium are not discussed.
Taking too much magnesium often leads to diarrhea. For some people this can happen with amounts as low as 350–500 mg per day. More serious problems can develop with excessive magnesium intake from magnesium-containing laxatives. However, the amounts of magnesium found in nutritional supplements are unlikely to cause such problems. People with kidney disease should not take magnesium supplements without consulting a doctor.