The symptoms of gastritis resemble those of cardiac arrhythmias. An ECG measures the electrical activity of the heart over time. The ECG involved strapping on electrodes to the chest of the patient and recording the cardiograms. It helps to determine whether cardiac muscles are damaged. When dyspepsia and heartburns occur, there is a need to identify the actual cause. The ECG helps to determine whether it is a cardiac problem or gastritis. As the pathogen causing gastritis breaks down urea, the urine also could be tested. Both, urine testing and ECG, are non-invasive tests and while the ECG is done only once, urine tests may be repeated to check the progress.

Blood tests are often done to determine the type of gastritis that the patient is suffering from. These are invasive tests and as they help in determining a variety of diagnoses, they may have to be repeated. If phlegmonous gastritis is suspected, the blood test will reveal the infectious agent. Similarly, blood tests could help in determining the presence of parietal cell bodies (implying atrophic gastritis) or intrinsic factor antibodies (implying pernicious anemia or autoimmune gastritis).

Gastritis often expresses as blood in stools. When this is noticed, the stool tests can be prescribed. Naturally, the test is non-invasive and painless for all it involves is a stool sample. Monoclonal and polyclonal assays are possible and each of the tests have great sensitivity and specificity for the H pylori bacteria. The stool tests are repeated to check the progress. Bismuth and antibiotics are known to interfere with this test. Therefore, they must be withheld before conducting the test.

If the gastritis has been caused due to autoimmune reasons, it is called atrophic gastritis. This disorder leads to reduced vitamin B 12 absorption which further leads to pernicious anemia. This deficiency of B 12 shows as depression, dementia, unexplained neurological disease and angular cheilitis. This is an invasive test that needs to be done only once. Blood is taken from a vein and then tested for the presence of the vitamin. There is only a pricking sensation when the test is done and even that little pain is gone in a few minutes after the test.

This test is popular as barium swallow. Barium is radioactive and shows well in an X-Ray. This non-invasive test involves taking a series of X-Rays of the upper gastrointestinal tract, thus revealing images of the esophagus, stomach and the small intestine. All the patient needs to do is to swallow a white liquid that contains barium. The ulcers show up clearly in the X-Ray. This test is often repeated to test the efficacy of the treatment.

Gastritis affects the upper gastrointestinal tract. Endoscopy allows the doctor to closely examine the lining of the esophagus, stomach and the small intestine. A hollow tube that is equipped with a lens is run along the esophagus into the stomach and small intestine. The doctor can examine the lining and mucosa on an external monitor. In case there are inflamed areas, small tissue samples (biopsy) can also be removed. While the endoscopy helps in assessment of the gastric mucosa, biopsy helps the histological assessment of the H pylori infection. This test is considered in patients who are refractory to treatment. So, it is mostly used for patients who are above 55 years of age. The test may be done repeatedly to check for progress.

Infection with Helicobacter pylori bacteria is one of the foremost causes of gastritis. Thus, testing its presence in the gastrointestinal tract would be a good diagnostic test. The non-invasive breath test is often used to detect this bacteria. The patient is made to drink a solution of urea which has been spiked with radioactive carbon. H pylori breaks down the urea into ammonia and carbon dioxide. Thus, the patient harboring bacteria in the gastrointestinal tract will show radioactive carbon in the breath sample.