Magnesium oxide is a mineral supplement that is used to prevent and treat low levels of magnesium in the blood. It is also used to treat symptoms of too much stomach acid such as heartburn, sour stomach, or acid indigestion. Magnesium oxide is available without a prescription and can be taken as a tablet or capsule by mouth. It is also used as a laxative for short-term, rapid emptying of the bowel before surgery, for example. Magnesium oxide is important for the normal functioning of cells, nerves, muscles, bones, and the heart. It is sometimes prescribed as a dietary supplement when the amount of magnesium in the diet is not enough. Magnesium oxide has been shown to offer several benefits, including potentially lowering blood pressure and blood sugar levels, treating chronic constipation, and relieving headaches. However, it is important to note that there are potential side effects to consider, and it is best to talk with a physician or a nutritionist before taking magnesium or using it for long periods.