Magnesium 250 mg Tablets, 100 ct, QC95909 Sale! This item is currently on backorder but you can still purchase it now and we'll ship as soon as more become available. Magnesium is essential for nerve and muscle function, and for converting blood to energy. Necessary for the metabolism of calcium, Vitamin C, phosphorus, sodium, and potassium. Natural, no added yeast, sugar, lactose, preservatives, artificial colors or flavors, and gluten-free.