Magnesium supplements like any supplement, if it’s not derived from a food source, it’s synthetic and not readily used by the body. It is possible (and toxic) to get too much magnesium from supplements
Too much magnesium is almost impossible if it comes from food or through the skin.
The following are the 8 adverse effects of excess magnesium supplementation:
1. Diarrhea (magnesium is a laxative, hence milk of magnesia)
3. Muscle weakness
5. Kidney dysfunction
6. Difficulty breathing
7. Heart attack (in extreme cases)
Important note: The Food and Nutrition Board of the Institute of Medicine advises against magnesium supplementation if you have any problems with your kidneys. The upper limit of daily magnesium intake via supplement is 350mg for adults. Less than that doesn’t cause trouble in most people.