The most common diagnostic test for gastritis is endoscopy with a biopsy of the stomach. The doctor will usually give the patient medicine to reduce discomfort and anxiety before beginning the endoscopy procedure. The doctor then inserts an endoscope, a thin tube with a tiny camera on the end, through the patient’s mouth or nose and into the stomach. The doctor uses the endoscope to examine the lining of the esophagus, stomach, and first portion of the small intestine. If necessary, the doctor will use the endoscope to perform a biopsy, which involves collecting tiny samples of tissue for examination with a microscope.

Other tests used to identify the cause of gastritis or any complications include the following:

• Upper gastrointestinal (GI) series. The patient swallows barium, a liquid contrast material that makes the digestive tract visible in an x ray. X-ray images may show changes in the stomach lining, such as erosions or ulcers.
  
• Blood test. The doctor may check for anemia, a condition in which the blood’s iron-rich substance, hemoglobin, is diminished. Anemia may be a sign of chronic bleeding in the stomach.
  
• Stool test. This test checks for the presence of blood in the stool, another sign of bleeding in the stomach.
  
• Tests for H. pylori infection. The doctor may test a patient’s breath, blood, or stool for signs of infection. H. pylori infection can also be confirmed with biopsies taken from the stomach during endoscopy.

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