Low Stomach Acid: The Symptoms, The Causes, And How To Test It At Home

If you are struggling with bloating, reflux, indigestion, chronically low iron or feel like you just aren't absorbing the nutrients out of your food properly, you want to read this.

Does any of this sound familiar?

You drink one glass of water and feel bloated for the rest of the day.

You feel heavy and overly full for hours after a meal that was not large, you get reflux or indigestion most nights, and you struggle to keeo your iron level up no matter how much red meat you eat or how many iron supplements you take (and an iron infusion only provides support for a short amount of time). 

Low stomach acid is one of the most common findings I see in clinic, and one of the most missed, because it produces almost exactly the same symptoms as too much acid.

Most women assume the burning and the bloating mean their stomach is producing too much, so they reach for something to reduce it, and the underlying problem gets worse over the following years.

Below I have covered what your stomach acid is doing, what happens when you are not making enough of it, how medications like Nexium and Somac affect production, the nutrient deficiencies that both cause it and are caused by it, and A REALLY SIMPLE TEST, you can do at home to see where your stomach acid is at.

What your stomach acid is doing

Your stomach should be extremely acidic, with a pH of 1.5 to 3.5. That is technically acidic enough to dissolve metal, and your body needs to maintain it at this level because your stomach acid is doing five really important jobs at once:

• Activating pepsin. Your stomach releases an inactive enzyme called pepsinogen, and hydrochloric acid converts it into pepsin, which is what breaks down dietary protein into amino acids. Without acid, protein arrives in your small intestine in large fragments that your body cannot utilise properly and can irritate your gut lining.

• Killing what comes in with your food. Bacteria, yeast, and parasites are dealt with in the stomach before they reach your intestines. Adequate acid is your first line of defence against gut infections and against bacteria colonising the small intestine (SIBO and other forms of microbiome dysbiosis).

• Signalling your pancreas. Acidic food arriving in the first section of your small intestine is the trigger for your pancreas to release lipase, protease, and amylase (which are three important enzymes that breakdown carbohydrates, proteins and fats. Weak acid means a weak signal, which means low enzyme release.

• Signalling your gallbladder. The same acidic signal contributes to the release of bile, which emulsifies fat so it can be digested, carries fat soluble vitamins A, D, E and K across the gut wall, and carries used oestrogen out of your body. Bile is also needed to bind to cholesterol, hormones and other toxins to clear them out (so if you aren't making enough bile, this can contribute to high cholesterol and hormonal imbalances).

• Making minerals absorbable. Iron, zinc, calcium, magnesium, selenium, B12, folate and vitamin C all require an acidic stomach environment to be liberated from food and broken down for absorption.

You can take every supplement on the shelf and eat a perfect diet, and if you are not producing enough acid you will not digest it properly. The nutrients in your food are the raw materials your body uses to repair itself, so when absorption is compromised, everything that depends on those nutrients starts to suffer.

Symptoms of low stomach acid (hypochlorhydria)

The clinical term is hypochlorhydria. These are the presentations I see most often:

• Bloating that starts within 30 to 60 minutes of eating, sometimes after nothing more than a glass of water

• Feeling heavy, full and uncomfortable for hours after a normal sized meal, as though the food has not moved

• Reflux, heartburn, or burning behind your sternum, often worse lying down at night

• Burping straight after meals, or excessive gas

• Undigested food visible in your stools

• Nausea after eating, particularly after protein or fat

• Constipation, loose stools, or alternating between the two

• Iron deficiency that will not resolve, or resolves on infusion and slides straight back down

• B12 at the low end of range, with fatigue, tingling in the hands or feet, and low mood

• Brittle nails, white spots on the nails, and hair shedding

• Very little appetite in the morning, feeling you could easily skip breakfast

• Bad breath

• Recurring thrush, gut infections, or a SIBO diagnosis

• Acne, eczema, or rosacea that keeps flaring

The single most useful signal in that list is the combination of digestive symptoms plus a nutritional deficiency that really struggles to improve.  Women who eat well, supplement consistently, and still cannot lift their ferritin are almost always dealing with an absorption problem rather than an intake problem.

What high stomach acid looks like

In eight years of clinical practice, genuine acid excess is something I see very rarely. When it does present, it looks like burning pain on an empty stomach that improves once you eat, forceful burping and froth or foaming at the back of the throat during the burp test, and a gurgling sensation in the upper abdomen.

The causes worth knowing about are H. pylori infection (which can raise or lower acid depending on where in the stomach it colonises), Zollinger-Ellison syndrome (a rare gastrin secreting tumour), and rebound acid hypersecretion after stopping a proton pump inhibitor abruptly, which I have covered further down.

Why low acid causes reflux

At the top of your stomach there is a valve called the lower oesophageal sphincter, and that valve needs a certain level of acidity to close and stay closed. When acid production drops, the valve does not seal completely, and the small amount of acid that is present splashes upward into your oesophagus, where the lining has no protection against it and burns.

So the burning tells you acid is in the wrong place, but it doesn't tell you there is too much of it.

Acid suppressing medication is appropriate and necessary in plenty of clinical situations, including gastric and duodenal ulcers, Barrett's oesophagus, H. pylori eradication protocols, and protecting the stomach lining alongside long term NSAID use. What I see in clinic is women who were prescribed it for symptoms assumed to be excess acid, stayed on it for six or eight years, and gradually developed the deficiencies described below.

What causes low stomach acid

Stress, by a long way. This is number one, and most of the women I work with do not describe themselves as stressed. They describe themselves as busy. Sitting in sympathetic nervous system mode all day sends blood away from your digestive organs and towards your muscles, and it reduces the vagal signalling that tells your parietal cells to produce acid. Your body treats digestion as a low priority when it thinks you are dealing with a threat, and a full inbox at 9pm reads to your physiology the same way a genuine threat does. Eating in the car, eating at your desk, and eating while scrolling all suppress acid production before the food even arrives.

Age. Parietal cell function declines gradually, and low stomach acid becomes considerably more common in women from around 35 onward, which is the same window in which perimenopausal changes begin.

Zinc deficiency. Your parietal cells need zinc to manufacture hydrochloric acid, because zinc is a required cofactor for carbonic anhydrase, the enzyme that supplies the hydrogen ions. Zinc itself requires an acidic stomach to be absorbed. So low zinc reduces acid production, and reduced acid lowers zinc absorption further, and the deficiency feeds itself. I see this cycle most often in women who have been on the oral contraceptive pill, women who have been chronically stressed for years, and women who have been on acid suppressing medication, because all three deplete zinc.

H. pylori infection. A bacterial infection of the stomach lining that can suppress acid production and damage parietal cells over time. Worth testing when clinically useful, particularly with persistent reflux, nausea, or unexplained iron deficiency.

Hypothyroidism. Thyroid hormone influences gastric acid secretion, so an underactive thyroid frequently comes with low stomach acid attached. And because low acid reduces absorption of the selenium, zinc, iron and iodine your thyroid requires, this is another self reinforcing cycle.

Chronic dieting and low protein intake. Protein is the trigger for acid secretion, so years of low protein eating gradually reduces production.

Autoimmune atrophic gastritis. An autoimmune condition where antibodies attack the parietal cells directly, reducing acid and intrinsic factor production. It has a strong association with Hashimoto's thyroiditis and with pernicious anaemia.

Alcohol, which irritates the gastric lining, and eating too fast, which skips the cephalic phase of digestion entirely.

How medications affect stomach acid

Three groups of medications reduce stomach acid, and they work in different ways.

Proton pump inhibitors (PPIs). Esomeprazole (Nexium), pantoprazole (Somac), omeprazole (Losec, Acimax), rabeprazole (Pariet), and lansoprazole (Zoton). These block the hydrogen-potassium ATPase pump in your parietal cells, which is the final step in acid production, so they shut off secretion at the source. They can reduce gastric acid output by more than 90 percent and the effect lasts well beyond a single dose. Most are approved for short courses of four to eight weeks, and a lot of women I see have been taking one daily for years without a review.

H2 receptor antagonists. Famotidine, cimetidine, and ranitidine (withdrawn in Australia in 2020). These block histamine at the H2 receptors on parietal cells, which reduces the stimulus to produce acid. Weaker and shorter acting than a PPI.

Antacids. Mylanta, Gaviscon, Quick-Eze, Rennie. These neutralise acid that has already been produced rather than reducing production, so the effect is immediate and short lived, and frequent use gradually reduces your capacity to digest protein and absorb minerals.

What long term acid suppression is associated with:

• Vitamin B12 deficiency, because acid and pepsin are required to release B12 from the protein it is bound to in food

• Iron deficiency, because non-haem iron needs an acidic environment to be converted from the ferric form into the ferrous form your body can absorb

• Low magnesium, with documented cases of significant hypomagnesaemia after 12 months or more of PPI use

• Reduced calcium absorption and an associated increase in hip, wrist and spine fracture risk in long term users

• Increased risk of small intestinal bacterial overgrowth (SIBO) and of Clostridioides difficile infection, because acid is your barrier against organisms reaching the intestines

• Reduced zinc absorption, which feeds straight back into the cycle described above

The rebound effect is worth understanding. When acid is suppressed for eight weeks or longer, your body increases gastrin production to compensate. Stop the medication suddenly and acid secretion rebounds above where it started for two to four weeks, which feels like proof that you needed the drug all along. A tapered withdrawal managed with your GP avoids most of that.

To be clear about this, because it is important: I am not telling anyone to stop a prescribed medication. That is a conversation for you and your GP, and stopping abruptly on your own is how people end up back on it for another five years. What I do suggest is asking for a medication review if you have been on a PPI for longer than a few months, and asking for iron studies, B12, and magnesium to be checked at the same time.

Other medications worth knowing about: metformin depletes B12, the oral contraceptive pill depletes zinc, B6 and magnesium, NSAIDs damage the gastric and intestinal lining directly, and corticosteroids reduce mucosal integrity.

The nutrient deficiencies that reduce stomach acid

• Zinc. Required for carbonic anhydrase and therefore for hydrochloric acid production. Oysters, beef, lamb, pumpkin seeds and oats are the strongest food sources.

• Vitamin B1 (thiamine). Involved in the parietal cell energy production that acid secretion depends on, and depleted quickly by alcohol, refined carbohydrates and chronic stress.

• Chloride and sodium. Hydrochloric acid is hydrogen and chloride, and chloride comes largely from dietary salt. Very low salt eating over a long period reduces the raw material available.

• Protein, specifically histidine. Histidine is the amino acid your body converts into histamine, and histamine binding to the H2 receptor is one of the main signals telling your parietal cells to secrete acid.

• Vitamin B6, required for the conversion of histidine into histamine.

The nutrient deficiencies that low stomach acid causes

• Iron. Non-haem iron from plant foods arrives in the ferric (Fe3+) form and needs stomach acid to be reduced to the ferrous (Fe2+) form your intestines can absorb. This is the mechanism behind the iron deficiency that will not resolve regardless of how much red meat or how many supplements you take.

• Vitamin B12. Acid and pepsin release B12 from dietary protein so that intrinsic factor can bind it for absorption in the terminal ileum. Low acid means B12 stays bound and passes straight through.

• Zinc. As above, and the cycle compounds year on year.

• Calcium and magnesium. Both require an acidic environment for solubility and absorption.

• Selenium and iodine. Both required for thyroid hormone production and conversion.

• Folate. Absorption is pH dependent.

• Vitamin C. Reduced absorption, which further reduces iron absorption, because vitamin C is one of the main enhancers of non-haem iron uptake.

• Amino acids. Without pepsin activation, protein is not cleaved into the amino acids your body uses to build muscle, hormones, neurotransmitters, enzymes, collagen, and the gut lining itself.

When to see your GP

Do not self diagnose your way past something that needs investigating. Book in with your GP if you have unintended weight loss, difficulty or pain on swallowing, persistent vomiting, black or tarry stools, vomiting blood, anaemia without an obvious cause, a family history of gastric cancer, or reflux that has been persistent for more than a few weeks. Testing for H. pylori, iron studies, B12, and coeliac serology are all worth asking about when clinically useful, and reflux that has gone on for years warrants a proper look rather than another repeat script.

Frequently asked questions

How accurate is the burp test? It is a useful home indicator rather than a validated diagnostic test. The gas produced is a genuine chemical reaction between bicarbonate and hydrochloric acid, so the result tells you something, but variables like how much water you use, how fast you drink it, and how much air you swallow all affect the timing. Run it three mornings in a row and look at the average.

Can you do the burp test while taking Nexium or another PPI? You can, and the result will show very low acid, because that is exactly what the medication is designed to do. It tells you the drug is working rather than telling you about your baseline production.

Does low stomach acid cause reflux? Frequently, yes. The lower oesophageal sphincter requires adequate acidity to close and stay closed, so when acid production drops the valve does not seal completely and the acid that is present travels upward into the oesophagus, where it burns.

How long does it take to improve stomach acid production? Digestive symptoms like bloating and heaviness after meals often improve within two to four weeks with consistent food and lifestyle changes. Correcting the downstream deficiencies takes longer, because ferritin and B12 rebuild over months rather than weeks.

Can low stomach acid cause low iron? Yes, and it is one of the most common reasons iron will not lift. Non-haem iron requires an acidic stomach environment to be converted into the form your intestines can absorb, so without adequate acid, the iron in your food and in your supplements passes through largely unabsorbed.

Is low stomach acid more common in women? It becomes considerably more common in women from around 35 onward, and the contributing factors stack up: years on the oral contraceptive pill depleting zinc, chronic stress suppressing secretion, thyroid dysfunction, and long term acid suppressing medication.

Where to start

If you recognised yourself in the symptom list, the order I work in is the burp test across three mornings, then food and lifestyle support for acid production, nervous system regulation from day one, and correcting the deficiencies once I know what your iron studies, B12 and zinc are doing.

I work with women worldwide through telehealth as a naturopath and nutritionist, and an initial consultation covers your full history, the symptoms you have stopped mentioning because nobody took them seriously, and a plan that treats the reason your acid production dropped rather than handing you a supplement to take with meals forever. You can find out more and book here

The Busy Women's Health Club 6-Week Reset covers gut health in Week 2, including stomach acid, enzymes and bile, with meal plans and recipes built around protein at every meal and the bitter foods that stimulate acid production. If you want the food side handled for you without the cost of one to one care, that is where to look.

If you do nothing else after reading this, start with the three slow breaths before you eat and the 30 chews per mouthful. Both are free, both use signalling pathways your body already has, and a week is long enough to know whether they change how you feel after dinner.

This article is general information, not personalised clinical advice. Speak to your GP or a qualified practitioner about your own circumstances, and never stop a prescribed medication without medical supervision.