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Classification and external resources
Hydrogen chloride (major component of gastric acid)
ICD-10 K31.8
ICD-9 536.0
DiseasesDB 29513
eMedicine med/18
MeSH D000126

Achlorhydria /klɔərˈhdriə/ or hypochlorhydria refers to states where the production of gastric acid in the stomach is absent or low, respectively. It is associated with various other medical problems.

Signs and symptoms[edit]

The decreased acid level itself can cause symptoms similar to gastroesophageal reflux disease, and impairs protein digestion by inhibiting the activation of the enzyme pepsin, whose activation is dependent upon a low gastric pH. Furthermore, low acid (high pH) levels in the stomach are linked with bacterial overgrowth (as the stomach does not kill microbes normally present in food), which can manifest as diarrhea or decreased absorption of nutrients or vitamins. Risk of particular infections, such as Vibrio vulnificus (commonly from seafood) is increased. Even without bacterial overgrowth, low stomach acid (high pH) can lead to nutritional deficiencies through malabsorption of basic electrolytes (magnesium, zinc, etc.) and vitamins (including vitamin C, vitamin K, and the B complex of vitamins). Such deficiencies may be involved in the development of a wide range of pathologies, from fairly benign neuromuscular issues to life-threatening diseases. A person with achlorhydria can suffer from stomach pains caused by the digestion of food that is not properly broken down by gastric acid.



Gastric analysis by radio telemetry is used to measure stomach acid and diagnose hypochlorhydria/achlorhydria, this test is often referred to as the "Heidelberg test".

90% of all patients with achlorhydria have detectable antibodies against the H+/K+ ATP-ase proton pump. The diagnosis is made if the gastric pH remains high (>4.0) despite maximum pentagastrin stimulation. High gastrin levels are often detected.


Treatment focuses on addressing the underlying cause of symptoms. With Helicobacter pylori induced achlorhydria, antibiotic treatment is usually prescribed, though it may not always reverse the condition completely.[2]


Little is known on the prognosis of achlorhydria, although there have been reports of an increased risk of gastric cancer.[3] A 2007 review article noted that non-Helicobacter bacterial species can be cultured from achlorhydric (pH > 4.0) stomachs, whereas normal stomach pH only permits the growth of Helicobacter species. Furthermore, experiments with achlorhydric mice have shown that non-Helicobacter bacteria can induce atrophic gastritis, which, in turn, can cause gastric carcinoma.[4]

See also[edit]


  1. ^ El-Omar EM, Oien K, El-Nujumi A et al. (1997). "Helicobacter pylori infection and chronic gastric acid hyposecretion". Gastroenterology 113 (1): 15–24. doi:10.1016/S0016-5085(97)70075-1. PMID 9207257. 
  2. ^ Iijima, K.; Sekine, H.; Koike, T.; Imatani, A.; Ohara, S.; Shimosegawa, T. (2004). "Long-term effect of Helicobacter pylori eradication on the reversibility of acid secretion in profound hypochlorhydria". Alimentary Pharmacology and Therapeutics 19 (11): 1181–1188. doi:10.1111/j.1365-2036.2004.01948.x. PMID 15153171.  edit
  3. ^ Svendsen JH, Dahl C, Svendsen LB, Christiansen PM (1986). "Gastric cancer risk in achlorhydric patients. A long-term follow-up study". Scand. J. Gastroenterol. 21 (1): 16–20. doi:10.3109/00365528609034615. PMID 3952447. 
  4. ^ Fox JG, Wang TC (2007). "Inflammation, atrophy, and gastric cancer.". J Clin Invest. 117 (1): 60–69. doi:10.1172/JCI30111. PMC 1716216. PMID 17200707.