Antacids are the type of medicines used for treating indigestion. Antacids are substances that help neutralize excess stomach acid, providing relief from symptoms like heartburn, upset stomach, and indigestion. They work by raising the pH of the stomach acid and reducing its acidity, which can alleviate the discomfort associated with indigestion. Common ingredients in antacids include aluminum hydroxide, magnesium hydroxide, calcium carbonate, and sodium bicarbonate.