Your child has too much magnesium in their blood. This is called hypermagnesemia. This can happen if a child's kidneys are failing. It also can be caused by medicines that contain magnesium, such as laxatives, antacids, or magnesium salts. A baby can be born with this problem if too much magnesium was taken during pregnancy. In the hospital, treatments are given to lower blood magnesium levels. Here's what you need to know to care for your child at home.