Gastric hypochlorhydria, or achlorhydria, refers to a decrease in hydrochloric acid secretion in the stomach. Its causes include gastric bypass surgery, Helicobacter pylori infection, proton pump inhibitor use, or pernicious anemia.

Patients with gastric hypochlorhydria undergo replacement of the usual gastric mucosa by intestinal-type cells, which may lead to cellular atypia and neoplasia. Patients with gastric hypochlorhydria may present with anemia, bloating, or vitamin deficiencies.

Gastric hypochlorhydria occurs equally across sexes and races and increases in prevalence with age. An association with intestinal metaplasia has also been established.