Omeprazole Side Effects: What Long-Term Use Really Does

Omeprazole is one of the most-prescribed drugs on earth, and most people who take it feel nothing at all. Short term, the common complaints are headache, nausea, diarrhoea, constipation, bloating and abdominal pain — each affecting 3% to 7% of users in the manufacturer’s trials U.S. Food and Drug Administration, PRILOSEC (omeprazole) Prescribing Information, 2012. That’s genuinely mild for a drug this widely used.

The long-term picture is where most of what you’ll read online turns alarmist or dismissive. Honestly: years of omeprazole use is associated with lower vitamin B12 and magnesium, modestly more hip fractures and chronic kidney disease, more gut and possibly chest infections, and — on stopping — a genuine rebound in acid production. Most of those associations are small, most come from observational data that can’t prove cause, and the one large randomised trial of a PPI taken for three years found almost nothing Moayyedi et al., Gastroenterology, 2019.

So this isn’t a hit piece. If you have erosive oesophagitis or Barrett’s, omeprazole is doing real work. But if you’re on it indefinitely for throat symptoms it was never likely to fix, you’re accumulating small risks in exchange for very little — which is where a lot of people reading this are. Here’s what the evidence actually says, risk by risk.

Key Takeaways

• Short-term side effects are mild: headache (7%), abdominal pain (5%), nausea and diarrhoea (4% each).
• Two or more years of PPI use was linked to a 65% higher rate of vitamin B12 deficiency in a large case-control study.
• Low magnesium is rarer but can cause cramps, palpitations and dizziness — pooled data suggest roughly a 1.8-fold increased risk.
• Hip fracture risk is about 20% higher in PPI users, yet bone density studies show no meaningful bone loss — a strong hint that confounding is doing the work.
• Acute interstitial nephritis is uncommon and usually reversible; the chronic kidney disease link rests on observational data only.
• The dementia evidence is genuinely mixed: a huge Danish cohort found an association, but meta-analysis and Mendelian randomisation do not support causation.
• Infection risk rises modestly — SIBO is the most consistent finding, while randomised trials have not confirmed the C. difficile signal.
• Stopping suddenly causes rebound acid hypersecretion: 44% of healthy volunteers developed reflux symptoms after eight weeks on a PPI, versus 15% on placebo.
• The biggest problem for most readers here isn’t side effects — it’s years on omeprazole for LPR, where it often doesn’t work well anyway. Never stop a prescribed PPI on your own; taper with your doctor, diet and barrier measures in place first.

How Omeprazole Works — And Why That Explains the Side Effects

Almost every long-term side effect here follows from one fact: omeprazole doesn’t calm your stomach, it switches off the pumps that acidify it. It binds those pumps irreversibly, so gastric pH rises from around 1.5–2 to somewhere between 4 and 6 for most of the day.

That’s the point of the drug, and for an ulcerated oesophagus it’s exactly right. But stomach acid isn’t only there to cause you grief. It liberates vitamin B12 from food protein, helps you absorb magnesium, calcium and iron, and kills much of the bacteria you swallow. Turn it down for years and you’d expect exactly what the research shows: nutrient absorption drifts, and gut bacteria get an easier ride.

Two other consequences matter. Low acid triggers more gastrin, which slowly grows the acid-producing cells — the setup for rebound when you stop. And omeprazole changes how acidic your reflux is, not whether it happens, which is why it disappoints so many people with throat symptoms. I’ve unpacked that in why PPIs don’t work for LPR; if you’re early in treatment, how long omeprazole takes to work is worth reading first.

Common Short-Term Side Effects

In the pooled clinical trial data behind omeprazole’s licence, the adverse reactions reported at 2% or more were headache (7%), abdominal pain (5%), nausea (4%), diarrhoea (4%), vomiting (3%) and flatulence (3%) U.S. Food and Drug Administration, PRILOSEC (omeprazole) Prescribing Information, 2012. Constipation, dizziness and rash appear at lower rates. Three practical notes:

• They’re often transient. Headache and nausea tend to settle over the first week or two, so it’s worth waiting out rather than abandoning the trial on day three.
• The placebo rates are close. People on dummy pills report headache and abdominal pain at similar frequencies, so some of what gets blamed on omeprazole is background noise — and some is the reflux itself.
• Bloating and wind are the most under-reported. Less acid means more surviving bacteria fermenting in the upper gut — a real mechanism, covered in acid reflux and gas.

Timing affects both effectiveness and tolerability, which I’ve covered separately in the best time to take omeprazole.

Vitamin B12 Deficiency

This is the best-established nutritional effect, and the mechanism is clean. Vitamin B12 in food arrives bound to protein, and stomach acid and pepsin release it so it can be absorbed further down. Suppress acid for long enough and less B12 gets liberated — while B12 in supplements, which isn’t protein-bound, is absorbed normally.

In a case-control study of nearly 26,000 people with newly diagnosed B12 deficiency compared with over 184,000 without, two or more years of PPI use was associated with a 65% increase in the odds of deficiency, and the association was stronger at higher doses Lam et al., JAMA, 2013.

How worried should you be? Moderately, mostly if you’re older, vegetarian or already borderline. Deficiency creeps up over years and produces fatigue, brain fog, pins and needles and low mood — symptoms easy to blame on something else. The fix is simple: get a serum B12 test after a couple of years on omeprazole, and supplement if it’s low or low-normal. Iron follows the same logic, so check ferritin too. The wider picture is in supplements for LPR.

Magnesium Deficiency (Hypomagnesaemia)

Low magnesium is rarer than low B12 but more likely to actually make you feel ill, which is why regulators issued a specific safety warning about it. One systematic review and meta-analysis found PPI use associated with roughly a 1.8-fold increase in the odds of hypomagnesaemia, while noting substantial variation between studies Cheungpasitporn et al., Renal Failure, 2015. Later reviews have landed somewhat lower, but still elevated.

It matters more than the number suggests because magnesium sits underneath a lot of body systems. Symptoms include muscle cramps and twitching, fatigue, palpitations, dizziness, and in severe cases seizures or arrhythmias. It also drags potassium and calcium down with it, which is why it’s sometimes only spotted when a stubbornly low potassium refuses to correct.

Those most at risk are on omeprazole for years, especially alongside diuretics or in older age. If you’re getting unexplained cramps, twitchy eyelids or palpitations, ask for a magnesium level — it isn’t on a standard blood panel and won’t be checked unless someone requests it. Palpitations in particular get blamed on the reflux so often that the drug never gets considered; more in acid reflux and heart palpitations.

Bone Density and Fracture Risk

Here the honest answer is more reassuring than the headlines. The association is real and reproducible: a meta-analysis of observational studies found PPI users had about a 20% higher risk of hip fracture than non-users Poly et al., Osteoporosis International, 2019, with similar or slightly larger effects for spine and any-site fractures elsewhere.

But here’s the puzzle. If omeprazole were weakening bone, you’d expect bone density to fall in people who take it. Mostly, it doesn’t. A meta-analysis of bone mineral density studies found no statistically significant difference in the annualised rate of bone loss between PPI users and non-users Aleraij et al., Bone Reports, 2020. And in the three-year randomised trial of pantoprazole versus placebo, fractures were no more common on the drug Moayyedi et al., Gastroenterology, 2019.

Fractures up, bone density unchanged: that strongly suggests something other than the drug is doing the work. People on long-term PPIs are, on average, older, heavier, on more medications and in worse general health — all of which independently predict falls and fractures. That’s textbook confounding by indication, and a 2025 systematic review concluded that confounding and bias limit what can be inferred across kidney, dementia and fracture outcomes alike Chaudhry et al., Cureus, 2025.

Practical take: an older adult with existing osteoporosis risk on unreviewed long-term omeprazole should have a conversation about it. If you’re 40 and otherwise healthy, it isn’t worth losing sleep over.

Kidney Disease: Interstitial Nephritis and CKD

There are two separate kidney issues here and they get muddled constantly.

Acute interstitial nephritis is an immune reaction in the kidney — an allergic response to the drug rather than dose-related toxicity. It’s uncommon, can appear weeks or months after starting, and often shows up as vague malaise, nausea and reduced urine output rather than anything obviously kidney-shaped. In a cohort of over 290,000 older adults starting a PPI matched against the same number of non-users, acute kidney injury occurred at 13.5 versus 5.5 per 1,000 person-years Antoniou et al., CMAJ Open, 2015. A doubling in relative terms — but look at the absolute numbers. It stays uncommon, and it’s usually reversible on stopping.

Chronic kidney disease is the bigger headline and the weaker evidence. In two large cohorts, PPI use was associated with incident CKD, with a hazard ratio of about 1.5 in the ARIC cohort and higher risk suggested with twice-daily dosing Lazarus et al., JAMA Internal Medicine, 2016. But it’s observational, the same confounding applies, and the randomised pantoprazole trial found no excess CKD over three years.

My read: the nephritis risk is small but real, while the CKD association is causally unproven. Neither justifies stopping a drug you genuinely need. Both justify not staying on one you don’t.

Dementia: What the Evidence Actually Shows

This is the claim that frightens people most, so let’s be specific rather than dramatic. The strongest observational signal comes from a nationwide Danish study of 1,983,785 people aged 60 to 75, followed from 2000 to 2018, during which there were 99,384 cases of dementia. PPI use was associated with a higher rate of dementia, and the association was strongest in the youngest group: an incidence rate ratio of 1.36 for dementia diagnosed at ages 60–69, falling to 1.12 at 70–79, 1.06 at 80–89, and 1.03 (not significant) at 90 and over. Longer treatment duration was associated with higher rate ratios Pourhadi et al., Alzheimer’s & Dementia, 2024.

That sounds alarming. Here’s the rest of the picture.

First, the age pattern argues against causation. If a drug damaged the brain, you’d expect its effect to persist or grow in the oldest and most vulnerable, not fade out. A risk appearing only in early-onset dementia looks more like a marker of something else — and early dementia has a long prodromal phase in which people develop exactly the sort of vague gastrointestinal symptoms that get treated with a PPI. That’s reverse causation, and it’s very hard to rule out.

Second, pooling weakens it considerably. A systematic review, meta-analysis and bias analysis covering more than 3.3 million people across nine cohorts found a relative risk of 1.16 (95% CI 1.00–1.35) — just short of significance, with enormous heterogeneity. The authors concluded the data did not indicate that PPI use increases dementia risk Ahn et al., British Journal of Clinical Pharmacology, 2023.

Third, researchers have tested this genetically. Mendelian randomisation uses inherited genetic variants as a natural randomisation, sidestepping the confounding and reverse causation that plague observational work. Applied to five PPI types and six dementia subtypes, the initial signals disappeared once corrected for multiple testing, and the authors concluded there was no robust causal relationship — adding that it would be inappropriate to restrict clinically justified prescriptions over cognitive concerns Xie et al., Scientific Reports, 2024.

So: an association exists in some large datasets, it doesn’t survive pooling well, and the genetic evidence doesn’t support causation. If you’ve been quietly worrying about your memory, the evidence doesn’t support omeprazole as the cause. What it does support is the boring conclusion running through this article — don’t stay on it for years without anyone asking whether you still need it.

Infection Risk from Reduced Stomach Acid

Stomach acid is an antimicrobial barrier. Raise gastric pH and more of what you swallow survives the journey. The question is how much that matters.

Small intestinal bacterial overgrowth (SIBO)

This is the most consistent finding, and the one causing the most day-to-day misery. A 2025 systematic review and meta-analysis of 29 studies found SIBO in 36.8% of PPI-treated patients versus 19.9% of controls (OR 2.14) Khurmatullina et al., Journal of Clinical Medicine, 2025.

SIBO produces bloating, burping, wind and abdominal discomfort — and here’s the cruel bit: that bloating raises intra-abdominal pressure and can make reflux worse, so the drug treating your reflux ends up feeding a mechanism driving it. If bloating worsened after starting omeprazole, read SIBO and acid reflux and gut health and acid reflux.

C. difficile and pneumonia

Observational studies have long linked acid suppression to Clostridioides difficile. A dose-response meta-analysis found a positive association overall but no strong evidence of a clean dose-response relationship Finke et al., Journal of Infection, 2025, while a meta-analysis restricted to randomised trials — eight trials, 29,880 participants — found no significant difference between PPI and control groups Floria et al., Gut Microbes, 2025. When observational studies and trials disagree, the trials usually win; the realistic risk is small and concentrated in hospitalised, antibiotic-exposed patients.

Pneumonia follows the same shape. A systematic review of 33 studies and meta-analysis of 26 found roughly a 1.5-fold increased risk of community-acquired pneumonia with outpatient PPI therapy Lambert et al., PLOS ONE, 2015. Again the randomised data don’t show it, and risk clusters in the first month of use — suggesting people were prescribed a PPI because they were already becoming unwell.

Rebound Acid Hypersecretion: The Side Effect Nobody Warns You About

If you take one thing from this article, make it this, because it’s the side effect most likely to trap you.

Suppressing acid raises gastrin, and sustained high gastrin gradually increases the mass of acid-producing tissue in your stomach. Withdraw the drug and those pumps come back online into a stomach that now has more of them than it started with. Acid output overshoots.

The demonstration is startling. In a randomised, double-blind, placebo-controlled study, 120 healthy volunteers with no reflux symptoms took either esomeprazole for eight weeks followed by four weeks of placebo, or placebo throughout. After stopping, 44% of the previously symptom-free drug group developed clinically significant heartburn, acid reflux or dyspepsia, versus 15% of the placebo group Reimer et al., Gastroenterology, 2009. The drug created reflux symptoms in people who never had them, purely by being stopped. Eight weeks was enough.

The consequence is a self-reinforcing trap. You try to come off omeprazole, symptoms flare within days, you conclude you still need it, and you restart. Nothing in that sequence tells you the drug was treating an underlying problem — it may simply be treating the rebound it caused. This is the single biggest reason people stay on PPIs for a decade.

The way out is a slow, planned taper rather than a hard stop, with the supportive measures already running before you start reducing. I’ve set out the full step-by-step process, timelines included, in getting off PPIs and acid rebound. Don’t attempt it unsupervised, and not at all without your doctor’s input if you’re being treated for erosive oesophagitis or Barrett’s.

Putting the Risks in Proportion

A list of risks read in isolation always looks worse than the reality, so here’s the counterbalance.

The strongest evidence on PPI safety is a randomised trial. 17,598 people took pantoprazole 40 mg daily or placebo for a median of three years, with data collected every six months on pneumonia, C. difficile, other enteric infections, fractures, gastric atrophy, chronic kidney disease, diabetes, dementia, cardiovascular disease, cancer, hospitalisation and death. The only signal reaching significance was a small increase in enteric infections, 1.4% versus 1.0% Moayyedi et al., Gastroenterology, 2019. Three years isn’t twenty — but it’s the closest thing to a clean answer we have, and it points firmly towards “mostly safe.”

It’s also worth saying what omeprazole is good at. For erosive oesophagitis it heals tissue H2 blockers often can’t, and PPIs remain the medical treatment of choice for GERD in current guidelines — guidelines that simultaneously acknowledge concerns about overprescribing Katz et al., The American Journal of Gastroenterology, 2022. A recent evidence-based review strikes the right balance: PPIs are effective and broadly safe for proper indications, but a large share of prescriptions have no ongoing indication at all, and deprescribing should be routine Andrawes et al., Medicina, 2025.

That’s the crux. The problem isn’t omeprazole. It’s omeprazole prescribed once and never reviewed.

The Real Problem for Silent Reflux Sufferers

The risk-benefit calculation for any drug depends entirely on the benefit side. If omeprazole is healing an ulcerated oesophagus, a 20% relative increase in hip fracture risk is a trivial price. If it’s doing nothing measurable for your throat clearing, hoarseness and globus sensation, then any risk is a bad deal — you’re paying a cost for nothing.

And in laryngopharyngeal reflux, PPIs frequently do very little. The reason is mechanical: they change the pH of what refluxes rather than stopping the reflux, and the main agent injuring the larynx is pepsin, which stays active well above the pH a PPI achieves. I’ve laid out the trial evidence in full — including the positive studies — in why PPIs don’t work for LPR and proton pump inhibitors for LPR.

What I see over and over: someone on omeprazole for years for throat symptoms, never reviewed, never offered anything else, now afraid to stop because the one time they tried, everything flared within a week. That flare was almost certainly rebound. The drug wasn’t working — but stopping it hurt, so it looked like it was. Worth flagging too: some people’s reflux involves low stomach acid rather than high, covered in does low stomach acid cause acid reflux.

What to Do If You’ve Been on Omeprazole for Years

None of this is a reason to panic or stop your medication today. It’s a reason to review it properly:

1. Establish why you’re on it. Erosive oesophagitis, Barrett’s, a bleeding-risk indication or Zollinger-Ellison syndrome are genuine long-term indications. “Started it in 2019 and never stopped” is not.
2. Get the relevant bloods. Serum B12, magnesium, ferritin and kidney function. Magnesium won’t be checked unless you ask.
3. Fix the inputs first. Dietary acidity, meal size and timing, late eating, alcohol and excess abdominal weight all drive how often reflux happens — the variable the drug doesn’t touch.
4. Add a physical barrier. An alginate raft sits on the stomach contents and physically blocks reflux — a completely different mechanism from acid suppression. See alginates for acid reflux.
5. Review your other medications. Plenty of common drugs relax the lower oesophageal sphincter or irritate the oesophagus — see medications that make acid reflux worse.
6. Discuss alternatives with your doctor. H2 blockers work differently and are often used to bridge a taper — see famotidine vs omeprazole and alternatives to famotidine. Newer potassium-competitive acid blockers are covered in Voquezna (vonoprazan) for acid reflux, and the full landscape in the best medication for LPR.
7. Then taper, slowly and supervised — not before the rest is in place. Full process in getting off PPIs and acid rebound. If you’ve already tried the obvious things and nothing has shifted, acid reflux medication not working covers what comes next.

The Bottom Line

Omeprazole’s long-term side effects are real, but smaller and less certain than the internet suggests. Lower B12 and magnesium are genuine and easily monitored. The fracture, kidney and dementia associations come almost entirely from observational data that struggles to separate the drug from the kind of person who takes it — and where randomised trials and genetic studies have looked, those signals have largely faded. Rebound on stopping is the one effect that’s unambiguous, and it’s routinely mistaken for proof you still need the drug.

The message isn’t “omeprazole is dangerous.” It’s that the risks, small as they are, only make sense if the drug is buying you something. For erosive oesophagitis or Barrett’s, it clearly is. For years of unreviewed use aimed at throat symptoms it was never suited to treating, it clearly isn’t. What changes things is working on how often reflux happens rather than only how acidic it is — and the biggest lever is what you eat and drink. That’s harder than it sounds, because acidity hides where you’d never guess: citric acid in packaged food, vinegar in sauces, carbonation, almost all fruit. The Wipeout Food Reference Guide is the essential companion for exactly that — the allowed and avoid lists for acid reflux and LPR with their real pH values, so you’re working from numbers rather than guesswork.

And if you’d rather have the whole thing sequenced properly — what to change, in what order, how long to give each stage, and how to reintroduce foods once things settle — the Wipeout Diet Plan goes considerably deeper. It was built first and foremost around LPR and silent reflux, the stubborn throat-based form that most often defeats medication, but because it works on the same underlying mechanisms it does just as much for GERD, heartburn and ordinary acid reflux. Whatever you decide about the drug, make it a decision you’ve actually reviewed with your doctor — and never stop a PPI abruptly on the strength of an article.

Frequently Asked Questions

What are the most common side effects of omeprazole?

Headache is the most frequently reported at around 7%, followed by abdominal pain (5%), nausea and diarrhoea (4% each), and vomiting and flatulence (3% each). Constipation, dizziness and bloating also occur. Most are mild and settle within the first week or two.

Is it safe to take omeprazole long term?

For a genuine indication such as erosive oesophagitis or Barrett’s oesophagus, yes — the benefits clearly outweigh the small risks. The largest randomised trial, following nearly 18,000 people for three years, found no significant harm apart from a small increase in enteric infections. The concern is long-term use without a current indication or any review.

Does omeprazole cause dementia?

The current evidence does not support causation. A large Danish cohort found an association, strongest for dementia diagnosed before age 70, but pooled meta-analysis of over 3.3 million people found the risk estimate just short of statistical significance, and Mendelian randomisation using genetic data found no robust causal link. Reverse causation is a plausible explanation for the observational findings.

Why do my symptoms get worse when I stop omeprazole?

Rebound acid hypersecretion. Acid suppression raises gastrin, which increases acid-producing tissue over time, so acid output overshoots when the drug is withdrawn. In a placebo-controlled study, 44% of healthy volunteers with no prior reflux developed symptoms after stopping just eight weeks of treatment. It’s a withdrawal effect, not proof you still need the drug.

Does omeprazole cause bloating and gas?

It can. Reduced acid allows more bacteria to survive and ferment in the upper gut, and pooled data show small intestinal bacterial overgrowth in around 37% of PPI users versus 20% of controls. The awkward part: bloating raises intra-abdominal pressure, which can worsen reflux.

How do I safely come off omeprazole?

Slowly, with your doctor, and after the supporting measures are already in place. That usually means sorting out dietary acidity, meal timing and an alginate first, then stepping the dose down over weeks — sometimes alternating days or bridging with an H2 blocker — rather than stopping outright. Never stop abruptly, and never stop without medical advice if you’re being treated for oesophageal damage.

Research & References

• U.S. Food and Drug Administration, PRILOSEC (omeprazole) Prescribing Information, 2012 — Pooled clinical trial data listing adverse reactions occurring at 2% or more: headache 7%, abdominal pain 5%, nausea 4%, diarrhoea 4%, vomiting 3% and flatulence 3%.
• Moayyedi et al., Gastroenterology, 2019 — Randomised trial of pantoprazole 40 mg versus placebo in 17,598 participants over a median of three years; no significant difference in pneumonia, fractures, chronic kidney disease, dementia, cancer or death, with the only significant signal a small increase in enteric infections (1.4% vs 1.0%).
• Katz et al., The American Journal of Gastroenterology, 2022 — ACG clinical guideline for GERD, confirming PPIs as the medical treatment of choice while acknowledging concerns about adverse events, long-term safety and overprescribing.
• Andrawes et al., Medicina, 2025 — Evidence-based review of PPI indications, efficacy and harms, concluding that PPIs are effective for proper indications but frequently continued without ongoing justification, and that deprescribing should be routine.
• Lam et al., JAMA, 2013 — Case-control study of 25,956 patients with incident vitamin B12 deficiency versus 184,199 controls; two or more years of PPI use was associated with a 65% increase in the odds of deficiency, with a dose relationship.
• Cheungpasitporn et al., Renal Failure, 2015 — Systematic review and meta-analysis of observational studies finding PPI use associated with a pooled odds ratio of approximately 1.78 for hypomagnesaemia, with significant heterogeneity between studies.
• Poly et al., Osteoporosis International, 2019 — Meta-analysis of observational studies finding PPI users had a 20% higher risk of hip fracture than non-users (RR 1.20, 95% CI 1.14–1.28), with the authors cautioning about inappropriate PPI use.
• Aleraij et al., Bone Reports, 2020 — Systematic review and meta-analysis of observational studies finding no statistically significant difference in annualised percentage change in bone mineral density between PPI users and non-users.
• Lazarus et al., JAMA Internal Medicine, 2016 — Analysis of the ARIC cohort (10,482 participants) and a Geisinger replication cohort (248,751 participants) finding PPI use associated with incident chronic kidney disease (adjusted HR 1.50 in ARIC), with higher risk suggested for twice-daily dosing.
• Antoniou et al., CMAJ Open, 2015 — Population-based cohort of 290,592 older adults starting a PPI and an equal number of matched controls; acute kidney injury occurred at 13.49 versus 5.46 per 1,000 person-years, with an increased rate of acute interstitial nephritis, though absolute risks remained low.
• Pourhadi et al., Alzheimer’s & Dementia, 2024 — Nationwide Danish cohort of 1,983,785 people aged 60–75 with 99,384 dementia cases; PPI ever-use was associated with incidence rate ratios of 1.36 at ages 60–69, 1.12 at 70–79, 1.06 at 80–89 and 1.03 at 90+, with longer treatment duration yielding higher ratios.
• Ahn et al., British Journal of Clinical Pharmacology, 2023 — Systematic review, meta-analysis and bias analysis of nine cohorts covering 3,302,778 people; the pooled relative risk for dementia was 1.16 (95% CI 1.00–1.35) with very high heterogeneity, and the authors concluded the data did not indicate that PPI use increases dementia risk.
• Xie et al., Scientific Reports, 2024 — Mendelian randomisation study of five PPI types against all-cause dementia and five subtypes; initial signals did not survive correction for the false discovery rate, and the authors concluded there is no robust causal relationship between PPI use and dementia.
• Chaudhry et al., Cureus, 2025 — Systematic review of long-term PPI use and kidney disease, dementia and fractures, concluding that many studies were limited by confounding and bias and could not establish causality, and recommending periodic reassessment and deprescribing where appropriate.
• Khurmatullina et al., Journal of Clinical Medicine, 2025 — Systematic review and meta-analysis of 29 studies finding small intestinal bacterial overgrowth in 36.8% of PPI-treated patients versus 19.9% of controls (OR 2.14).
• Finke et al., Journal of Infection, 2025 — Systematic review and dose-response meta-analysis of PPIs and Clostridioides difficile infection, finding a positive association overall but no strong evidence of a dose-response relationship.
• Floria et al., Gut Microbes, 2025 — Meta-analysis of eight randomised controlled trials including 29,880 participants, finding no significant difference in Clostridioides difficile infection between PPI and control groups (RR 1.19, 95% CI 0.75–1.89).
• Lambert et al., PLOS ONE, 2015 — Systematic review of 33 studies and meta-analysis of 26 finding roughly a 1.5-fold increased risk of community-acquired pneumonia with outpatient PPI therapy, with risk concentrated in the early period after starting treatment.
• Reimer et al., Gastroenterology, 2009 — Randomised, double-blind, placebo-controlled trial in 120 healthy volunteers; after eight weeks of esomeprazole followed by withdrawal, 44% developed clinically significant acid-related symptoms versus 15% on placebo, demonstrating rebound acid hypersecretion.