Dr. Hymen writes, “I remember using magnesium when I worked in the emergency room. It was a critical "medication" on the crash cart. If someone was dying of a life-threatening arrhythmia (or irregular heart beat), we used intravenous magnesium. If someone was constipated or needed to prepare for colonoscopy, we gave them milk of magnesia or a green bottle of liquid magnesium citrate, which emptied their bowels. If pregnant women came in with pre-term labor, or high blood pressure of pregnancy (pre-eclampsia) or seizures, we gave them continuous high doses of intravenous magnesium.”
The standard you will read: Oral magnesium supplementation is safe in adults when used in dosages below the upper intake level of 350 mg per day (elemental magnesium). However, higher dosages have been studied and may be used.
Magnesium supplementation is safe in adults when used at almost any dose. Unless one has advanced kidney disease the kidneys will clear excess magnesium from the blood. For most people the worst that can happen is that one will get diarrhoea, which will have the effect of cleaning out the colon, not a bad thing in and of itself, especially if one’s tendency is toward constipation.