Most individuals with chronic gastritis or duodenitis have no symptoms. On the other hand, some people develop more serious problems, including stomach or duodenal ulcers. Ulcers can cause a variety of symptoms or no symptoms at all. Common complaints include pain or discomfort (usually in the upper abdomen), bloating, feeling full after eating a small amount of food, lack of appetite, nausea, vomiting, and dark or tar-colored stools. Ulcers that bleed can cause a low blood count and fatigue.
Less commonly, chronic gastritis causes abnormal changes in the stomach lining, which can lead to certain forms of cancer. It is uncommon to develop cancer as a result of H. pylori infection. Nevertheless, because so many people in the world are infected with H. pylori, it is considered to be an important cause of stomach cancer.