Low stomach acid — known medically as hypochlorhydria (and, when acid is essentially absent, achlorhydria) — is a reduction in the hydrochloric acid your stomach normally produces. Because that acid does real work in digestion, having too little of it can show up as vague upper-gut discomfort and, over time, as trouble absorbing certain nutrients. Here is what stomach acid does, the signs people notice, what causes low acid, and an honest look at the popular at-home "tests."
This is general wellness information, not medical advice. Symptoms below are nonspecific and overlap with many common conditions — see a qualified healthcare provider for diagnosis.
What stomach acid actually does
Your stomach is not just a mixing bag. As the NIDDK puts it, "glands in your stomach lining make stomach acid and enzymes that break down food," and the stomach muscles "mix the food with these digestive juices." Acid is central to the first chemical step of digestion, especially for protein.
Clinically, gastric hydrochloric acid "plays an integral part in the digestion of food and protects our body against pathogens ingested with food or water." In other words, adequate acid both helps unlock nutrients and acts as a first line of defense against microbes that arrive with what you eat and drink.
Signs and symptoms of low stomach acid
The everyday complaints people report tend to be upper-gut and nonspecific: epigastric (upper-abdominal) discomfort, a heavy or over-full feeling after meals, bloating, and nausea. Because acid helps break down protein, some people notice that protein-heavy meals sit poorly.
The more meaningful, longer-term signals are nutritional. Reduced stomach acid is linked in the literature to iron deficiency, vitamin B12 deficiency, and vitamin D and calcium shortfalls, because acid helps liberate and absorb these nutrients. That is why persistent low acid is worth a proper workup rather than guesswork.
Note the honest overlap: many of these sensations — fullness, bloating, reflux-like discomfort — also occur with too much acid and with unrelated conditions. Symptoms alone cannot tell you which way your acid is running.
What causes low stomach acid?
- Aging. The incidence of reduced acid rises with age, increasing roughly threefold in people over 60.
- H. pylori infection. This common stomach bacterium can suppress the machinery that produces acid.
- Long-term acid-reducing medication. Extended use of proton pump inhibitors (PPIs) is linked to hypochlorhydria — which is the intended effect, but worth understanding if you take them for months or years.
- Autoimmune damage. In pernicious anemia, antibodies damage the acid-producing parietal cells.
The "baking soda test" and betaine HCl: an honest take
Search low stomach acid and you will meet the baking soda stomach acid test (drink baking soda in water, time how long until you burp) and betaine HCl supplements taken to "add acid." Be skeptical. The baking soda burp test has never been validated as a reliable measure of stomach acid — burp timing depends on how you swallow, meal timing, and chance, not just acidity. Accurate assessment of gastric acid is a clinical matter (for example, pH testing performed and interpreted by clinicians), not a kitchen experiment.
Betaine HCl is sold as a supplement, but self-dosing acid can irritate the stomach and is not a substitute for finding out why symptoms are happening. If you suspect low stomach acid, the right move is a conversation with a provider — especially before starting or stopping any acid-related medication.
Low acid, your gut bacteria, and where Flore fits
Stomach acid is also a gatekeeper for what reaches the rest of your gut. When acid is low, more live microbes survive the trip downstream, which can shift the balance of bacteria further along — part of why acid, digestion, and the microbiome are connected. (For the flip side — what happens when acid-reducers are overused — see our read on antacids and your gut.)
Downstream, those gut bacteria are the ones that ferment fiber into beneficial compounds like butyrate, a short-chain fatty acid that fuels the gut lining. If your digestion feels off and you want to understand your own gut community rather than guess, Flore (formerly Sun Genomics) sequences your microbiome and builds a personalized probiotic-and-prebiotic formula from your own data — wellness insight into your gut, not a medical diagnosis.
Flore (formerly Sun Genomics) builds personalized probiotics from your own gut microbiome. We run a CLIA/CAP-certified laboratory and use whole-genome sequencing — experience grounded in roughly a decade of work: ~18,392 customers, ~23,000 microbiome tests, and ~40,000 custom formulations, rated 4.4★ across ~318 reviews. That operating scale is what informs this article.
This is educational, structure/function information — not medical advice, and not intended to diagnose, treat, cure, or prevent any disease.
Frequently asked questions
What are the symptoms of low stomach acid (hypochlorhydria)?
Everyday symptoms are upper-gut and nonspecific: epigastric (upper-abdominal) discomfort, feeling over-full or heavy after meals, bloating, and nausea, with protein-heavy meals sometimes sitting poorly. Over the longer term, reduced acid is linked to iron deficiency, vitamin B12 deficiency, and vitamin D and calcium shortfalls, because acid helps liberate and absorb these nutrients. Because these overlap with many conditions (including too much acid), symptoms alone cannot confirm low acid.
What does stomach acid do?
Glands in your stomach lining make stomach acid and enzymes that break down food, and the stomach mixes food with these digestive juices (NIDDK). Gastric hydrochloric acid plays an integral part in digesting food and helps protect the body against pathogens ingested with food or water.
What causes low stomach acid?
Common causes include aging (incidence rises roughly threefold after age 60), H. pylori infection (which can suppress acid production), long-term use of proton pump inhibitors (PPIs), and autoimmune damage to acid-producing cells as seen in pernicious anemia.
How do you test for low stomach acid — does the baking soda test work?
The popular baking-soda burp test has never been validated as a reliable measure of stomach acid; burp timing depends on swallowing, meal timing, and chance, not just acidity. Accurate assessment is a clinical matter (for example, pH testing performed and interpreted by clinicians), not a kitchen experiment. See a provider rather than self-diagnosing.
Should I take betaine HCl for low stomach acid?
Betaine HCl is sold as a supplement, but self-dosing acid can irritate the stomach and does not address why symptoms are happening. It is not a substitute for a proper evaluation — talk to a healthcare provider, especially before starting or stopping any acid-related medication. This is general wellness information, not medical advice.
Can long-term antacids or acid reducers cause low stomach acid?
Yes — that is their purpose. Extended use of proton pump inhibitors is associated with hypochlorhydria. If you take acid reducers for months or years, it is worth discussing with your provider. For more on how acid-reducers affect the gut, see our article on antacids and your gut.
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Flore was formerly Sun Genomics. This article is general wellness information and is not medical advice, diagnosis, or treatment. Statements have not been evaluated by the FDA. Talk to a qualified healthcare provider about your health.