Achlorhydria: What It Means and Why You Shouldn't Worry

Achlorhydria: what it means and why you shouldn't worry. Achlorhydria is the complete absence of hydrochloric acid in the stomach, an uncommon condition mainly associated with atrophic gastritis, autoimmune diseases, and in some cases, chronic Helicobacter pylori infection.

What is achlorhydria?

Achlorhydria is a medical condition in which the stomach doesn't produce hydrochloric acid (HCl) or produces such low amounts that it practically doesn't fulfill any digestive function. It's the most extreme version of hypochlorhydria (which means "low acid").

To understand it better: stomach acid is like the "engine" of the stomach for digestion. When that engine completely shuts off, we call it achlorhydria.

What does stomach acid do?

Stomach acid has three main functions:

1. Protein digestion: Activates pepsin, the enzyme that breaks down proteins into smaller pieces.
2. Nutrient absorption: Necessary to absorb vitamin B12, iron, calcium, and magnesium.
3. Protective barrier: The acidic pH kills bacteria and pathogens that enter with food.

When acid is lacking, these three functions are compromised, and that's where potential consequences come from: B12 deficiency, iron deficiency anemia, and increased risk of intestinal infections.

Is achlorhydria common? (spoiler: no)

Reassuring Message

Achlorhydria is a rare condition in the general population. Most people, even with mild or moderate gastritis, maintain normal or slightly reduced stomach acid production.

Prevalence data in the general population

In an Asian study with routine gastroscopy and Congo red staining (a method to detect acid), the prevalence of achlorhydria was 0.53% in adults, and increased to 0.68% in those over 45 years old. ¹

In Western populations, studies with healthy controls show an approximate prevalence of 1.8%. ²

Practical translation:

Out of every 100 healthy adults, fewer than 2 will have achlorhydria. That is, it's very uncommon. And when it appears, it's usually in specific contexts: atrophic gastritis, autoimmune diseases, or chronic H. pylori infection.

What about people with pernicious anemia?

In patients with pernicious anemia (an autoimmune disease that destroys the stomach cells that produce acid), the prevalence of achlorhydria is much higher, but in the general population, permanent achlorhydria is rare and increases with age and the presence of autoimmune diseases. ¹ ²

Transient vs. permanent achlorhydria

Achlorhydria can be transient in the context of infections or acute gastritis (and recovers), or permanent when there's advanced atrophic gastritis, autoimmune, or from H. pylori. ¹ ²

Main causes of achlorhydria

1) Autoimmune atrophic gastritis (pernicious anemia)

This is the most classic cause. In this disease, the immune system attacks the parietal cells of the stomach (those that produce acid) and destroys them irreversibly. The result is permanent achlorhydria and vitamin B12 deficiency, because intrinsic factor production is also lost (necessary to absorb B12). ³ ⁴

2) Chronic Helicobacter pylori infection

H. pylori can induce multifocal atrophic gastritis over time. Chronic infection causes inflammation, parietal cell damage, and in some patients, can trigger achlorhydria. It has also been described that H. pylori can favor autoimmunity mechanisms against the proton pump of parietal cells. ⁵ ⁶

If you have H. pylori and you're concerned, here's a related article: Does Helicobacter pylori cause cancer? Find out here.

3) Prolonged use of proton pump inhibitors (PPIs)

Prolonged use of omeprazole and other PPIs can cause pharmacological achlorhydria, although it's generally reversible after stopping treatment. Cases of permanent achlorhydria from PPIs are rare and usually associated with underlying mucosal damage (for example, prior atrophic gastritis). ⁷

4) Other less common causes

Include gastrectomy (stomach surgery), Zollinger-Ellison syndrome treated with PPIs, and infiltrative or neoplastic diseases affecting the gastric mucosa. ⁷ ⁸

What symptoms does achlorhydria cause?

Here's the surprise: many people with achlorhydria are asymptomatic. They don't feel anything. Symptoms appear when there's nutrient deficiency or malabsorption:

Anemia from B12 deficiency: Fatigue, pallor, tingling in hands and feet.
Iron deficiency anemia: From poor iron absorption.
Heavy digestion: Feeling that "food doesn't move".
Increased risk of intestinal infections: From loss of acid's protective barrier.

If you have digestive discomfort but not achlorhydria, you might be interested in this article about other common gastrointestinal disorders.

How is achlorhydria diagnosed?

Diagnosis is not made with home tests (like the famous "baking soda and burp test," which has no scientific validity). Specific tests are required:

Validated diagnostic methods

• Congo red test during endoscopy: The stomach is stained with a dye that changes color according to pH. If there's no acid, it doesn't change color. ⁹
• Blood quininium resin test: Indirectly measures acid secretion. ¹⁰
• Augmented histamine test: Stimulates acid production and measures response. ¹¹
• Calcium carbonate breath test: A non-invasive method that measures stomach acid function. ¹²

In clinical practice, achlorhydria diagnosis is usually made in the context of an endoscopy with biopsies showing atrophic gastritis, and confirmed with blood tests showing B12 deficiency, anemia, and elevated serum gastrin levels (the body tries to compensate for lack of acid by producing more gastrin).

If you need quality endoscopy to evaluate your stomach, you can check our advanced endoscopy services.

Why you shouldn't worry (really)

Key Message

Achlorhydria is rare, has identifiable causes, and can be controlled with treatment and follow-up. Most people with achlorhydria are asymptomatic and have good quality of life with B12 and iron supplementation.

1) It's uncommon

As we saw before, prevalence in the general population is less than 2%. If you've been diagnosed with achlorhydria, you're probably part of a very specific group (atrophic gastritis, pernicious anemia, etc.).

2) It has known and treatable causes

If it's from H. pylori, the infection is treated. If it's from autoimmune gastritis, B12 is supplemented and monitored. If it's from PPIs, the need for treatment is reviewed. In all cases, there's something to do.

3) You can live well with achlorhydria

With vitamin B12 supplementation (oral or injectable) and iron, most people with achlorhydria maintain a normal life. Achlorhydria doesn't hurt or produce symptoms by itself; symptoms come from nutrient deficiency, and that's correctable.

4) It's monitored with periodic controls

Achlorhydria associated with atrophic gastritis can slightly increase the risk of gastric cancer, but that risk is controlled with follow-up endoscopies every 1-3 years depending on the case. If you want to know more about this topic, here's an article: Atrophic gastritis and cancer risk 2025.

Book an Appointment

If you have achlorhydria or suspect you might have it, we can evaluate it together in consultation with a complete assessment.

What follow-up does a person with achlorhydria need?

1. Periodic blood tests: Monitoring B12, iron, ferritin, complete blood count.
2. Supplementation: Vitamin B12 (oral or injectable depending on the case), iron if needed.
3. Follow-up endoscopy: Every 1-3 years if there's atrophic gastritis, to monitor precancerous changes (intestinal metaplasia, dysplasia).
4. H. pylori treatment: If present, it's eradicated to stop gastritis progression.

A personal touch (medicine is also human)

I understand that when you're told "achlorhydria" it sounds terrible. But the reality is that it's a rare condition, with clear causes, and can be controlled very well. My job is to remove the noise and keep what's useful: what it means, what needs to be monitored, and what steps make sense.

Selfie in operating room giving thumbs up

FAQ: Quick questions about achlorhydria

What exactly is achlorhydria?

It's the complete absence of acid in the stomach. The stomach doesn't produce hydrochloric acid or produces minimal amounts that don't fulfill digestive function.

Is achlorhydria common?

No. In healthy adults, prevalence is very low (0.5-1.8% according to studies). It increases with age and in people with autoimmune diseases or advanced atrophic gastritis. ¹ ²

Can omeprazole cause permanent achlorhydria?

Rarely. PPIs can cause reversible pharmacological achlorhydria. Permanent achlorhydria from PPIs is exceptional and usually associated with prior mucosal damage. ⁷

Does achlorhydria always cause symptoms?

Not always. Many people with achlorhydria are asymptomatic. Symptoms appear when there's B12 deficiency, anemia, or nutrient malabsorption.

Does the baking soda and burp test work to diagnose it?

No. That home test has no scientific validity. Diagnosis requires validated methods like Congo red test during endoscopy or specialized breath tests. ⁹

Does achlorhydria increase the risk of gastric cancer?

It can, especially if there's atrophic gastritis with intestinal metaplasia. That's why follow-up endoscopy every 1-3 years is recommended. But absolute risk remains low with proper surveillance.

References (clickable)

Phaosawasdi K, Sritunyarat Y, Lopimpisuth C, et al. BMJ Open Gastroenterology (2022). Prevalence of Achlorhydria in an Asian Population Detected Using Congo Red Staining During Routine Gastroscopy: 22 Years' Experience From a Single Centre. PubMed: 35580914
Betesh AL, Santa Ana CA, Cole JA, Fordtran JS. The American Journal of Clinical Nutrition (2015). Is Achlorhydria a Cause of Iron Deficiency Anemia? PubMed: 25733628
Vavallo M, Cingolani S, Cozza G, et al. International Journal of Molecular Sciences (2024). Autoimmune Gastritis and Hypochlorhydria: Known Concepts From a New Perspective. PubMed: 38983978
Hershko C, Patz J, Ronson A. Blood Cells, Molecules & Diseases (2007). The Anemia of Achylia Gastrica Revisited. PubMed: 17049280
Hodges P, Kelly P, Kayamba V. PloS One (2021). Helicobacter Pylori Infection and Hypochlorhydria in Zambian Adults and Children: A Secondary Data Analysis. PubMed: 34343178
Cater RE. Medical Hypotheses (1992). Helicobacter (Aka Campylobacter) Pylori as the Major Causal Factor in Chronic Hypochlorhydria. PubMed: 1435394
Griffith JL, Cummings OW, Hirschowitz BI. Gastroenterology (1991). Development of Sustained Achlorhydria in a Patient With the Zollinger-Ellison Syndrome Treated With Omeprazole. PubMed: 2060207
Fuchs CS, Mayer RJ. The New England Journal of Medicine (1995). Gastric Carcinoma. PubMed: 7666851
Tóth E, Sjölund K, Thorsson O, Thorlacius H. Gastrointestinal Endoscopy (2002). Evaluation of Gastric Acid Secretion at Endoscopy With a Modified Congo Red Test. PubMed: 11818934
De Martel C, Ratanasopa S, Passaro D, Parsonnet J. Digestive Diseases and Sciences (2006). Validation of the Blood Quininium Resin Test for Assessing Gastric Hypochlorhydria. PubMed: 16532391
Callender ST, Retief FP, Witts LJ. Gut (1960). The Augmented Histamine Test With Special Reference to Achlorhydria. PubMed: 14416401
Clough MR, Axon AT. European Journal of Gastroenterology & Hepatology (2009). The Calcium Carbonate Breath Test, a Noninvasive Test of Stimulated Gastric Acid Secretion: Preliminary Communication. PubMed: 19564802

Achlorhydria: What It Means and Why You Shouldn’t Worry | Patient Guide