Tums is an antacid made of sucrose (sugar) and calcium carbonate (CaCO3) manufactured by GlaxoSmithKline in St. Louis, Missouri, USA. They are also available sugar free. It is an over-the-counter drug and available at many retail stores, including drug stores, grocery stores and mass merchandisers. It provides relief from acid indigestion, heartburn, and indigestion ("sour stomach") and is considered a calcium supplement.