This medication is a mineral supplement used to prevent and treat low amounts of magnesium in the blood. Some brands are also used to treat symptoms of too much stomach acid such as stomach upset, heartburn, and acid indigestion. Magnesium is very important for the normal functioning of cells, nerves, muscles, bones, and the heart. Usually, a well-balanced diet provides normal blood levels of magnesium. However, certain situations cause your body to lose magnesium faster than you can replace it from your diet. These situations include treatment with "water pills" (diuretics such as furosemide, hydrochlorothiazide), a poor diet, alcoholism, or other medical conditions (such as severe diarrhea/vomiting, stomach/intestinal absorption problems, poorly controlled diabetes).