For most patients, gastritis improves quickly with treatment. Gastritis caused by medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) typically clears up when the medications are discontinued. Acute stress gastritis generally clears up when the illness, injury or stress that caused it is controlled. Medications and diet changes are usually all that is required for other forms of gastritis.

When gastritis symptoms are mild, antacids may effectively reduce or alleviate symptoms. These over-the-counter medications neutralize the hydrochloric acid in the stomach. They need to be taken several times a day and may cause diarrhea or constipation in some people.

Medications such as H2 blockers may also be used to reduce the production of stomach acid. Proton pump inhibitors block the action of the “pumps” in the cells that secrete acid. They are stronger than H2 blockers. Cytoprotective agents (medications that protect the stomach lining) may also be used to help ease and prevent irritation. Medications in these classes are available in both over-the-counter and prescription forms.

When gastritis is caused by an infection such as Helicobacter pylori, antibiotics are typically used. Two different antibiotics are generally required for one to two weeks. They are usually combined with a proton pump inhibitor and/or a cytoprotective agent. When gastritis is associated with pernicious anemia (low red blood cell count due to vitamin B12 deficiency), the patient may require lifelong supplemental injections of vitamin B12. Antiemetics and fluids may be prescribed if gastritis is accompanied by vomiting.

Physicians typically recommend a bland diet for patients with acute gastritis until the symptoms subside. Foods that cause stomach upset may need to be identified and eliminated from the diet, especially those that are spicy, acidic, fried or fatty. A high protein diet may be recommended for patients with Ménétrier's disease.

Most instances of bleeding in gastritis are minor, disappear on their own and do not require specific treatment. However, heavy, persistent bleeding may be dangerous. Though there are many options to treat this, few are effective in the long term. Blood transfusions may make the bleeding worse. Cauterization (heat-sealing) of bleeding points is possible during endoscopy, but it is often temporary and bleeding may eventually resume.