If you’ve been prescribed omeprazole for heartburn, reflux or stomach ulcers but now feel more gassy, bloated or uncomfortable, you’re not imagining it.

Gas (“farting more than usual”) is listed as a common side effect of omeprazole on NHS information pages. Many people also report new or worse bloating once they start a proton pump inhibitor (PPI) like omeprazole.

But why does a medication designed to soothe your stomach sometimes end up making it feel worse? And how do you know whether your symptoms are from the tablet, your underlying condition, IBS… or something like SIBO?

Let’s break it down in a clear, practical way.

Quick answer: can omeprazole cause gas and bloating?

Yes. Omeprazole can cause gas and bloating in some people.

• Flatulence (passing more wind) is a documented common side effect of omeprazole
• Studies of people taking PPIs find that bloating, abdominal discomfort, changes in bowel habit and flatulence are frequently reported.
• Longer-term PPI use is linked with a higher risk of small intestinal bacterial overgrowth (SIBO), which often causes significant bloating and gas.
•  However, not everyone reacts this way. For some, PPIs dramatically improve symptoms; for others, they create new problems. The key is understanding how omeprazole changes digestion and what to do if your gut isn’t happy.

Important: Never stop, change or reduce a prescribed medication without speaking to your GP, gastroenterologist or prescriber.

A pattern I often see in clinic is that patients start omeprazole for reflux, only to notice new bloating, gas, or abdominal discomfort soon after.

What is omeprazole and how does it work?

Omeprazole is a proton pump inhibitor (PPI) – a medicine that blocks the “proton pump” in the cells lining your stomach. This pump normally releases hydrochloric acid, which helps:

• break down proteins
• activate digestive enzymes
• control bacteria entering from food
• signal to the rest of the gut to move food along

By switching this pump off, omeprazole significantly reduces stomach acid production, which is why it’s often prescribed for: GORD / GERD (gastro-oesophageal reflux disease)

• recurrent heartburn and indigestion
• stomach or duodenal ulcers
• oesophagitis caused by acid

Short-term, that can be incredibly helpful. But long-term or high-dose acid suppression can have knock-on effects further down the digestive tract.

Why does omeprazole cause gas and bloating?

There are several ways omeprazole may contribute to excess wind, bloating and IBS-like symptoms.

Food isn’t broken down as efficiently

Stomach acid isn’t just there to cause heartburn – it’s also a key part of normal digestion.

With low acid:

• Proteins aren’t unfolded properly.
• Pepsin, a protein-digesting enzyme, isn’t activated as effectively.
• Food may leave the stomach less digested than usual.

Poorly digested food arriving in the small intestine is more likely to be fermented by bacteria, producing gas, bloating and sometimes loose stools.

This is one of the key reasons behind what many people describe as omeprazole stomach bloating, particularly after meals.

Slower stomach emptying and gut motility

Stomach acid helps trigger hormonal and nerve signals that tell your gut to keep things moving.

When acid is heavily suppressed:

• The stomach may empty more slowly, leaving you feeling painfully full, “pregnant-bloat” or distended after even normal-sized meals.
• Food may linger in the upper gut, which encourages fermentation and gas build-up.

Some people describe this as a “heavy brick in the stomach” feeling that wasn’t there before.. Changes in gut bacteria (dysbiosis and SIBO)

Acid is one of your body’s natural defences against excessive bacteria from food and the mouth. When acid levels are low for a long time, that protective barrier is weakened.

Research shows that PPIs:

• Increase bacterial counts in the upper gut, including the stomach and small intestine.
• Are associated with a moderately increased risk of small intestinal bacterial overgrowth (SIBO). Meta-analyses suggest an odds ratio of around 1.7 for SIBO in PPI users.
• Significantly alter the composition of the gut microbiome, and these changes are linked with PPI-related digestive problems such as functional dyspepsia, SIBO and C. difficile infection. Frontiers

SIBO commonly causes:

• marked bloating (often worse as the day goes on)
• excessive gas, sometimes foul-smelling
• abdominal pain or discomfort
• loose stools, urgency OR constipation

In other words, long-term omeprazole doesn’t directly “cause” gas in the way beans do – but by changing your digestive environment, it can set the stage for more fermentation, more gas and more bloating.

Increased susceptibility to infections

By reducing acid, PPIs can slightly increase the risk of certain gut infections (for example C. difficile), which may present with bloating, diarrhoea and pain.

This isn’t common, but it’s another reason your gut might feel worse on long-term PPIs, especially if symptoms are severe, watery or associated with fever.

Is it the omeprazole, IBS, or something else?

This is where things get confusing. The symptoms of:

• reflux / gastritis
• IBS
• SIBO
• food intolerances
• and omeprazole side effects

can all overlap.

Clues that omeprazole itself might be contributing to your gas and bloating include:

• Your bloating/gas started or significantly worsened soon after beginning omeprazole.
• Symptoms improve or lessen if the dose is reduced or temporarily paused (only ever under medical guidance).
• You notice more upper-abdominal bloating or fullness shortly after meals.
• You’ve been on a high dose or long course (months to years) and now have increasingly IBS-like symptoms.

Clues that something else is going on:

• Bloating and gas were severe well before omeprazole.
• You have a history of IBS, food poisoning, antibiotic overuse, coeliac disease, endometriosis or previous gut surgery.
• There are clear food triggers (e.g., gluten, dairy, high-FODMAP foods).
• You’re experiencing unintentional weight loss, blood in the stool, severe pain, difficulty swallowing, fever or vomiting – all red flags that need urgent medical assessment.

In practice, it’s often a combination: a sensitive gut, underlying IBS or SIBO, plus the acid suppression from omeprazole tipping things over.

How common are gas and bloating on omeprazole?

Large studies and real-world data suggest:

• Flatulence and other digestive complaints are common side effects of omeprazole, listed in NHS guidance.
• In one study of people on PPIs, over 80% reported bloating, and more than half reported excess gas.
• In multi-centre studies of PPI users, SIBO-type symptoms (bloating, abdominal discomfort, diarrhoea) first appeared after a course of PPIs in around 44% of cases.
•  So if you’re feeling more bloated on omeprazole, you’re not alone.

Practical ways to reduce gas and bloating while taking omeprazole

If you and your doctor decide you need to remain on a PPI, there’s still a lot you can do nutritionally and lifestyle-wise to reduce bloating and support your gut.

1. Review the basics: dose, timing, and how you take it

Discuss with your prescriber:

• Is your dose the lowest effective dose?
• Could a step-down (e.g., once daily instead of twice) or intermittent use be appropriate for you?
• Are you taking it exactly as advised (usually 30–60 minutes before food)?

Sometimes fine-tuning dose and timing can make a surprising difference.

Never alter your dose on your own. Always discuss changes with your GP or specialist.

2. Reduce common dietary gas-triggers

While you’re on omeprazole, your gut may be more sensitive to fermentable carbs:

• Trial a low-FODMAP–style approach (with professional support), especially reducing:
  • onions, garlic, leeks
  • apples, pears, stone fruits
  • beans, lentils, chickpeas
  • wheat-based bread and pasta
  • sugar alcohols (xylitol, sorbitol, mannitol, etc.)
• Limit fizzy drinks, sparkling water, beer and chewing gum (which add swallowed air).
• Avoid overeating and late-night heavy meals, which increase reflux and bloating.

3. Support digestion, not just suppress acid

Discuss with a practitioner whether the following are appropriate for you:

• Gentle digestive support such as bitters, ginger or carminative herbs – only if they don’t worsen reflux.
• Eating hygiene:
  • eat more slowly
  • chew thoroughly
  • avoid working or scrolling while eating
• Mindful eating and stress reduction around meals – stress itself slows gut motility and increases symptoms.

4. Address constipation (if present)

Gas and bloating are always worse if your bowels are sluggish.

• Aim for regular, complete bowel movements.
• Ensure adequate hydration and fibre from tolerated foods (e.g., oats, kiwi, ground flax if suitable).
• Gentle movement – walking after meals, light stretching – can stimulate motility.

5. Consider your microbiome

Because PPIs change the gut flora, it can help to support a healthy microbiome:

• Include fermented foods if tolerated (e.g., small amounts of live yoghurt, kefir, sauerkraut).
• Some people benefit from a tailored probiotic, but in SIBO-prone individuals this needs to be chosen carefully; the wrong strain can worsen gas and bloating.

·      

Could long-term omeprazole use have led to SIBO or dysbiosis?

If you’ve been on omeprazole or another PPI for months or years, and now have:

• severe bloating
• lots of gas
• IBS-like bowel changes
• brain fog or fatigue around meals

it’s reasonable to ask whether SIBO or dysbiosis is part of the picture.

Multiple studies and meta-analyses have found:

• PPIs are associated with increased bacterial growth in the stomach and small intestine.
• PPI use moderately increases the risk of SIBO, with odds ratios around 1.7.
• Symptoms characteristic of SIBO (bloating, abdominal pain, diarrhoea) often appear after a course of PPIs. Testing options you might consider discussing with your healthcare team include:
• Breath testing for SIBO (hydrogen/methane)
• Comprehensive stool testing (to look at colon microbiome, inflammation, digestive markers)

If SIBO or significant dysbiosis is found, a structured plan involving antibiotics or herbal antimicrobials, diet, motility support and careful probiotics may be more effective than simply staying on or off omeprazole.

Can changing or stopping omeprazole help bloating?

Sometimes, yes – but this needs to be done safely.

PPI rebound

Stopping PPIs suddenly can cause “rebound acid hypersecretion”, where stomach acid temporarily increases above baseline. This can flare reflux and make you feel worse, leading you to restart the medication.

A better-tolerated approach (if appropriate for your condition) often involves:

• Gradual tapering of the dose
• Introducing non-PPI strategies at the same time (diet, lifestyle, sometimes H2-blockers under medical supervision)
• Clear monitoring for alarm symptoms

This should always be guided by your GP, gastroenterologist or prescribing clinician, especially if you’ve had ulcers, Barrett’s oesophagus or other serious conditions where PPIs may be protective.

How functional medicine and nutrition can help

From a functional medicine perspective, the goal is to ask “Why is the acid there in the first place?”, rather than simply suppressing it indefinitely.

Depending on your history, a personalised plan may explore:

• Dietary triggers for reflux and bloating (fatty foods, caffeine, alcohol, chocolate, ultra-processed foods, large evening meals, etc.)
• Food intolerances (e.g., lactose, fructose, gluten) that are driving gas and distension
• SIBO or dysbiosis linked with long-term PPI use, antibiotics or gut infections
• Stomach acid insufficiency (hypochlorhydria) or low digestive enzymes in some patients – paradoxically, very low acid can produce reflux-type symptoms
• Motility issues (slow gut transit, post-infectious IBS)
• Stress and the gut–brain axis, which can amplify both reflux and IBS symptoms

By working through these layers, many clients can:

• Significantly reduce bloating and gas
• Improve bowel habits and energy levels
• In some cases, with their doctor’s support, reduce their reliance on long-term PPIs
  

Case Study: Bloating After Starting Omeprazole

A patient in her early 40s came to our clinic with persistent bloating and gas that had developed over the previous year.

She had been prescribed omeprazole for reflux, which she had taken for 10 years initially improved her heartburn. However, within a few months, she began to experience:

• Bloating after meals
• Increased gas
• Abdominal discomfort

She was advised to adjust her diet and try fibre supplements, but her symptoms continued.

Despite improvements in her reflux, she felt increasingly uncomfortable after meals, often describing her stomach as swollen and tight.

We arranged for her to complete a SIBO breath test

The results were positive and indicated that she had developed small intestinal bacterial overgrowth.

We implemented a targeted protocol, including herbal antimicrobials such as Oregano to address bacterial overgrowth, alongside a low fermentable diet.

Over the following weeks, her symptoms improved significantly, with a marked reduction in bloating and post-meal discomfort.

Case Study 2: Bloating and low Iron After Omeprazole

A 45-year-old man came to the clinic feeling frustrated and confused.

He had started taking Omeprazole for acid reflux, and initially it worked well. His heartburn improved, but within a few months she began to experience new symptoms including:

• Bloating and gas after most meals
• Persistent gas and abdominal discomfort
• Fatigue and low energy

We arranged a SIBO breath test and carried blood tests to assess iron and B12 levels.

The SIBO test was positive, and blood test showed Low levels of Vitamin B12 and Iron.

In his case, reduced stomach acid had likely created an environment that allowed bacterial overgrowth to develop, while also impairing the absorption of key nutrients.

We introduced a targeted plan including herbal antimicrobials, and iron and B12 supplements alongside a GP-led review of his medication.

Within a few months, his bloating improved significantly, along with his energy levels and overall digestion.

FAQs about omeprazole, gas and bloating

Does omeprazole cause smelly gas?

It can. When more food is fermented by bacteria rather than digested and absorbed, you may notice more frequent or stronger-smelling wind. This can be due to:

• increased bacterial activity in the small intestine
• changes in the types of bacteria present
• diets higher in fermentable carbohydrates while on PPIs

If your gas is extremely foul-smelling and accompanied by diarrhoea, pain or weight loss, seek medical advice.

How long does bloating last after starting omeprazole?

For some people, mild digestive side effects settle within a week or two as the body adjust. If your bloating:

• is severe,
• persists for more than a few weeks, or
• is getting steadily worse,

it’s worth discussing alternative options or further investigation with your doctor.

Will stopping omeprazole make my bloating go away?

Sometimes bloating improves once PPIs are reduced or stopped. But if SIBO, IBS or another condition has developed, symptoms may persist until these are dealt with directly.

This is why a combination of medical review and targeted gut-health support is often the most effective route.

Are there alternatives to omeprazole?

Depending on your diagnosis, your doctor may discuss:

• H2 blockers (like ranitidine alternatives or famotidine)
• Shorter courses of PPIs rather than long-term use
• On-demand use for known triggers
• Non-drug measures: weight loss where appropriate, elevating the head of the bed, avoiding late meals, reducing alcohol, smoking cessation, and tailored nutrition changes

Never switch or stop acid-suppressing medication without medical advice, especially if you’ve been treated for ulcers, Barrett’s oesophagus or severe oesophagitis.

Why does omeprazole make me gassy?

Omeprazole reduces stomach acid, which means food is not broken down as efficiently. This allows more fermentation by gut bacteria, leading to gas production. This is why many people notice increased wind, bloating, or discomfort after starting the medication.

Take-home message

• Yes, omeprazole can cause gas and bloating in some people. Flatulence is a recognised side effect, and bloating is commonly reported in PPI users.
• It does this mainly by reducing stomach acid, which:
  • impairs normal digestion
  • slows gut motility
  • alters gut bacteria and can increase the risk of SIBO and dysbiosis
• Not everyone reacts the same way. For some, omeprazole is life-changing; for others, it creates or worsens IBS-type symptoms.
• If you’re experiencing bothersome bloating or gas:
  • don’t stop your medication suddenly
  • speak to your GP or specialist about options
  • consider a functional, root-cause approach to assess your microbiome, motility, diet and triggers

With the right plan, it is absolutely possible to protect your oesophagus, manage reflux and dramatically reduce bloating and gas.

Why does Omeprazole cause bloating?

Omeprazole reduces stomach acid, which can impair digestion and allow bacteria to grow more easily in the gut. This can lead to increased fermentation of food, producing gas and causing bloating.

Does Omeprazole cause wind?

Yes, omeprazole can cause wind (gas). By lowering stomach acid, it may alter digestion and the balance of gut bacteria, which can result in increased gas production.

Does Omeprazole reduce B12 and Iron?

A growing body of research suggests that long-term use of proton pump inhibitors (PPIs) is associated with reduced levels of vitamin B12 and, in some cases, iron.

The degree of impact varies depending on:

• Duration of use
• Individual digestive function
• Dietary intake

However, several studies have linked prolonged PPI use with an increased risk of vitamin B12 deficiency and related symptoms, particularly in those taking these medications for extended periods.

Who Is Most at Risk of Bloating on Omeprazole?

While not everyone will experience side effects, certain individuals are more likely to develop bloating when taking Omeprazole.

You may be at higher risk if you:

Take omeprazole long-term

The longer stomach acid is suppressed, the greater the impact on digestion and the gut microbiome. Over time, this can increase the likelihood of bacterial overgrowth and fermentation, leading to gas and bloating.

Have Irritable Bowel Syndrome (IBS)

People with IBS often have a more sensitive digestive system and altered gut motility. This makes them more prone to bloating, particularly when digestion is further disrupted.

Have had food poisoning

A history of gastroenteritis can affect gut motility and increase the risk of developing Small Intestinal Bacterial Overgrowth (SIBO). In these cases, reducing stomach acid may further increase the risk of bacterial imbalance.

Experience chronic stress

Stress has a direct impact on digestion. It can reduce stomach acid production, slow gut motility, and alter the gut–brain axis — all of which can contribute to bloating.

Already experience digestive symptoms

If you already struggle with bloating, reflux, or food sensitivities, you may be more susceptible to worsening symptoms when taking PPIs.

👉 Key takeaway:
Omeprazole is more likely to cause bloating in individuals with underlying digestive vulnerabilities, particularly where gut function or microbiome balance is already compromised.

Struggling with Bloating?

If you are experiencing persistent bloating after meals, it may indicate an underlying issue such as SIBO, gut dysbiosis, or impaired digestion.

At our clinic, we take a personalised, root-cause approach to identify what is driving your symptoms.

Book a consultation to receive a tailored assessment and clear plan to support your digestive health. We offer consultations at our sister clinic ibs-solutions.co.uk

Our at-home SIBO breath test provides a simple and reliable way to assess hydrogen and methane gas production, helping to identify whether bacterial overgrowth in the small intestine is contributing to your symptoms.

Order your SIBO test today and take the first step towards understanding what is driving your bloating.

👉 [Order a SIBO Test]

References

National Health Service (NHS) (2023) Omeprazole: Side effects. Available at: https://www.nhs.uk/medicines/omeprazole/side-effects/ (Accessed: 24 March 2026).

Freedberg, D.E., Kim, L.S. and Yang, Y.X. (2017) ‘The risks and benefits of long-term use of proton pump inhibitors: Expert review and best practice advice’, Gastroenterology, 152(4), pp. 706–715.

Lo, W.K. and Chan, W.W. (2013) ‘Proton pump inhibitor use and the risk of small intestinal bacterial overgrowth: A meta-analysis’, Clinical Gastroenterology and Hepatology, 11(5), pp. 483–490.

Jackson, M.A. et al. (2016) ‘Proton pump inhibitors alter the composition of the gut microbiota’, Gut, 65(5), pp. 749–756.

Imhann, F. et al. (2016) ‘Proton pump inhibitors affect the gut microbiome’, Gut, 65(5), pp. 740–748.

Lombardo, L. et al. (2010) ‘Increased incidence of small intestinal bacterial overgrowth during proton pump inhibitor therapy’, Clinical Gastroenterology and Hepatology, 8(6), pp. 504–508.

Compare, D. et al. (2011) ‘Proton pump inhibitors and risk of small intestinal bacterial overgrowth: A systematic review’, Journal of Clinical Gastroenterology, 45(6), pp. 507–512.

Su, T. et al. (2018) ‘Meta-analysis: Proton pump inhibitors moderately increase the risk of small intestinal bacterial overgrowth’, Journal of Gastroenterology, 53(1), pp. 27–36.

Frontiers in Microbiology (2020) ‘Proton pump inhibitors and their effects on gut microbiota’, Frontiers in Microbiology, 11, p. 573.

Lippi, G. and Mattiuzzi, C. (2020) ‘Proton pump inhibitors and risk of Clostridium difficile infection’, Journal of Hospital Infection, 104(1), pp. 15–20.

Author – Victoria Tyler BSc Hons MBANT

Victoria Tyler owns and runs two busy clinics : Nutrition and Vitality and the IBS and Gut Disorder Clinic.

Nutrition and Vitality, along with the IBS and Gut Disorder Clinic, were founded with the goal of helping patients alleviate IBS symptoms by uncovering and addressing the root causes of their digestive issues.

As a Registered Nutritional Therapist, Victoria holds a BSc (Hons) in Nutritional Therapy and has trained with the Institute of Functional Medicine. She is also accredited by BANT and CNHC.

Before transitioning into health, Victoria earned a degree in Economics and an MBA, working with corporations including Canon and Vodafone. However, her own health challenges led her to pursue a career in Nutritional Therapy.

With a passion for learning, Victoria is committed to staying at the forefront of Functional Medicine. She helps patients manage IBS and other digestive disorders, including SIBO, Candida, and IBD, by identifying and addressing their root causes.

Victoria strongly believes that every symptom has an underlying cause, and there is always a solution to every health condition. To learn more, or to see patient reviews, visit Victoria’s profile on Google.

DISCLAIMER: The information provided in this article is intended for general informational purposes only and should not be construed as medical advice, diagnosis, or treatment. The products and methods mentioned are not a substitute for professional medical advice from a trained healthcare specialist. Always seek the guidance of your doctor or other qualified health professional with any questions you may have regarding your health or a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. Use of the information and products discussed is at your own risk.