Low pepsinogen 1 is an abnormal condition that suggests a decrease in gastric acid secretion, and is mainly seen in patients with chronic atrophic gastritis and those who have undergone gastrectomy. Pepsinogen is a precursor of pepsin, which is mainly categorized into pepsinogen 1 and pepsinogen 2. A low pepsinogen 1 value suggests the presence of insufficient gastric acid secretion or decreased gastric acid secretion, which can be seen in patients with chronic atrophic gastritis and may be associated with decreased gastric acid secretion after a major resection of the stomach. After the occurrence of low pepsinogen 1, it is necessary to further improve the gastroscopy and H. pylori test, and under the guidance of the doctor to give symptomatic drug treatment.