Untreated gastritis can result in a number of severe complications. Notable issues include the formation of ulcers in the stomach or small intestine, which can lead to intense pain and bleeding. There is also a heightened risk of developing stomach cancer, particularly linked to infections like Helicobacter pylori. Over time, chronic gastritis can evolve into atrophic gastritis, which might cause digestive problems and anemia due to vitamin B12 deficiency.