GastroTest measures stomach hydrochloric acid production in the body. This is done by the patient swallowing a capsule with a pH string inside – the string is pulled out once the capsule has been swallowed allowing me to measure the pH levels of the stomach, esophagus and mouth. Proper digestive secretion is important to measure proper protein breakdown in the body. Too little acid results in inadequate digestive secretion and poor digestion. Problems with stomach acid secretion can lead to gas and bloating, digestive pains, constipation, diarrhea and other symptoms of malabsorption. Most problems with the digestive system result in low acid rather than high acid. Even conditions such as heartburn are often a result of low stomach acid.