Achlorhydria denotes the absence of hydrochloric acid secretion by the stomach. It is distinct from hypochlorhydria, which refers to reduced acid output. Gastric acid plays a central role in digestion, inactivation of ingested microbes, and the absorption of certain nutrients, so its loss can lead to a broad range of clinical effects.

Causes and risk factors

  • Autoimmune gastritis — immune destruction of stomach lining cells that produce acid and intrinsic factor.
  • Chronic Helicobacter pylori infection — long-standing infection can damage acid-secreting tissue.
  • Medications — long-term proton pump inhibitors or H2-blockers may severely reduce acid; rarely this may approximate achlorhydria.
  • Surgical removal — gastric surgery that removes acid-producing regions of the stomach.
  • Age and other conditions — older adults and certain systemic illnesses may have diminished acid secretion.

Symptoms and complications

Symptoms are often nonspecific: bloating, indigestion, early satiety, and loose stools. Key complications arise from impaired digestion and microbial overgrowth. These can include nutrient deficiencies such as vitamin B12 and iron, increased susceptibility to enteric infections, and bacterial overgrowth in the small intestine. In autoimmune forms there is also an established link with pernicious anemia and a need for surveillance for gastric precancerous changes.

Diagnosis

Evaluation typically combines clinical history with targeted testing. Endoscopy with mucosal biopsies can identify atrophic gastritis or H. pylori. Measurement of gastric pH or tests that infer acid secretion may be used. Blood tests can show related abnormalities such as low B12 or elevated gastrin in some cases. Careful review of medication use is important because acid-suppressing drugs can mimic or cause low-acid states.

Management and prognosis

Treatment focuses on the underlying cause when possible: eradication of H. pylori if present, stopping or adjusting acid-suppressing therapy if appropriate, and monitoring or treating autoimmune disease. Nutritional management is often required — for example, vitamin B12 injections or oral supplementation and correction of iron deficiency. Addressing bacterial overgrowth or malabsorption can improve symptoms. Long-term follow-up may be recommended for certain causes to monitor complications.

Distinctions and notable facts

Remember that achlorhydria means virtually no gastric acid, while hypochlorhydria means reduced acid. Not all patients with low acid have obvious symptoms, and many features overlap with common digestive complaints. For concise clinical guidance or patient information see further reading.