If you’ve been told you have IBS but your symptoms aren’t improving, you’re not alone.

Many people experience ongoing bloating, gas, constipation, and digestive discomfort for months or even years without ever receiving a clear explanation for why.

In some cases, an underlying condition such as Small Intestinal Bacterial Overgrowth (SIBO) may not have been investigated by GPs, Doctors or the NHS at all.

Despite growing awareness, SIBO is still not routinely discussed in many GP consultations which means it can easily be missed as an underlying cause of IBS.

SIBO is a condition that many Doctors may not have never heard of and one that is not always routinely discussed when you visit your GP.

It is not uncommon to experience digestive symptoms for months or even years without SIBO ever being mentioned as a possibility.

This isn’t because your doctor isn’t trying to help. It reflects the way digestive conditions are typically assessed, where the focus is often on diagnosing IBS and managing symptoms, rather than investigating underlying causes.

You might find yourself wondering:

• Why am I still bloated all the time?
• Why am I not offered any tests?
• Could something have been missed?
  

One possible explanation is that an underlying condition such as SIBO has not been identified.

SIBO is increasingly recognised as a contributor to digestive symptoms, particularly in people diagnosed with IBS. Research suggests that around one in three people with IBS may have underlying bacterial overgrowth, although estimates vary depending on how it is tested.

However, in the UK, it is not always routinely investigated.

This means that many people continue to live with symptoms without ever being tested for one of the most common underlying causes.

What Is SIBO? A Simple Explanation

SIBO stands for Small Intestinal Bacterial Overgrowth.

Under normal conditions, the small intestine contains relatively low levels of bacteria compared to the large intestine. This is important, as the small intestine is primarily responsible for digestion and nutrient absorption.

However, when this balance is disrupted, bacteria can accumulate in the small intestine.

This can happen for several reasons, including:

• Slowed gut motility
• Structural changes in the digestive tract
• Previous infections or food poisoning
• Long-term use of medications such as omeprazole

When bacteria are present in excess, they ferment carbohydrates from the food you eat.

This produces gases such as hydrogen and methane, which can lead to symptoms including:

• Bloating (often shortly after eating)
• Excess gas or belching
• Abdominal discomfort or pain
• Diarrhoea or constipation
• Fatigue or brain fog
• Difficulty tolerating certain foods

Because these symptoms overlap significantly with IBS, SIBO is often not tested for or recognised as a separate condition.

If you suspect this may be affecting you, you can learn more about our SIBO testing here.

Can Your GP Test for SIBO in the NHS ?

Many people ask: can a GP test for SIBO?

In reality, most GPs cannot test for SIBO directly. While referral is sometimes possible, access to SIBO testing in the NHS UK is limited and varies by location.

In most cases, you would need to be referred to a gastroenterologist, which can involve significant waiting times.

In addition, SIBO testing is not routinely included in standard IBS pathways, meaning it may not be considered during initial assessment.

Access to testing also varies depending on where you live. Some NHS hospitals offer hydrogen and methane breath tests, while others do not routinely provide them at all.

This means that access to testing can depend on your local NHS trust and referral pathways.

As a result, many people are never tested even when symptoms persist.

Is SIBO Testing Available on the NHS?

Some NHS hospitals do offer breath testing for SIBO, but availability is not consistent across the UK.

In practice, testing is usually only accessible through a specialist referral, which can involve long waiting times. In addition, not all NHS trusts routinely provide SIBO testing, meaning access often depends on where you live.

For many patients, this can result in symptoms being managed without further investigation into potential underlying causes.

Because of this, some people choose to explore other testing options, particularly if their symptoms are ongoing or not improving. Breath testing can also be carried out outside of the NHS, including options that allow testing to be completed at home.

This type of testing can now be done conveniently at home. You can learn more about our SIBO TEST – this can be shipped all over the UK.

Why Doctors Don’t Diagnose SIBO

There is no single reason why SIBO is often missed. Instead, it reflects how digestive conditions are typically assessed within modern healthcare.

1. IBS Is a Diagnosis of Exclusion

IBS is usually diagnosed after more serious conditions have been ruled out, which is an essential step in ensuring nothing important is missed.

However, for many people, this is also where the process ends.

Once you’ve been given an IBS diagnosis, the focus often shifts to managing symptoms rather than investigating why they are happening in the first place.

As a result, underlying causes such as SIBO may never be explored.

2. NICE Guidelines

Another important factor is that SIBO is not currently a routine part of NICE (National Institute for Health and Care Excellence) guidelines for IBS.

When you present to your GP, your care is typically guided by these national recommendations.

NICE guidelines focus on:

• Diagnosing IBS based on symptom patterns
• Ruling out serious conditions
• Managing symptoms through diet and medication

At present, SIBO testing is not routinely included in these pathways.

This means that, in many cases, it may not be considered even if symptoms persist.

3. Symptoms Overlap With Many Conditions

One of the biggest challenges with SIBO is that its symptoms are not specific.

Bloating, abdominal pain, diarrhoea, and constipation can occur in many conditions, including:

• IBS
• Food intolerances
• Gut dysbiosis
• Candida
• Stress-related gut dysfunction
• Parasites
• Malabsorption

Because of this overlap, SIBO is often misdiagnosed as IBS.

In some cases, symptoms may also overlap with issues such as yeast overgrowth. You can read more in our article on does Candida cause bloating.

4. Limitations of SIBO Testing

Even when testing is available, it is important to understand that no test is perfect.

The most commonly used method is the hydrogen and methane breath test, which is non-invasive and widely used in both NHS and private settings.

However, results can be influenced by factors such as:

• Diet before the test
• Gut transit time
• Recent antibiotic use
• Individual differences in gas production

This means that results can sometimes be difficult to interpret.

What Is the Gold Standard Test?

The gold standard test for SIBO is a small bowel aspirate and culture, which involves taking a sample of fluid directly from the small intestine during an endoscopy.

While more accurate, this test is:

• Invasive
• Expensive
• Not widely available
• Rarely used in routine practice

For this reason, diagnosis is usually based on a combination of symptoms, clinical history, and breath testing.

Why SIBO Is Often Missed in the NHS

Although SIBO is recognised within gastroenterology, it is not routinely tested for within standard NHS pathways.

Most patients presenting with digestive symptoms are diagnosed with IBS and managed accordingly.

This means that:

• Underlying causes may not be identified
• Symptoms may persist despite treatment
• Patients may feel stuck without clear answers

What We See in Clinical Practice

In clinical practice, many of the patients we see have already been diagnosed with IBS, often for several years.

A common pattern is that symptoms began after a specific trigger, such as food poisoning, stress, or long-term use of medications like omeprazole, but this link is not always explored further.

Many patients have already tried multiple dietary approaches, including low FODMAP, gluten-free, or dairy-free diets, often with only partial or temporary relief.

In these cases, it is not uncommon to find that an underlying issue such as SIBO has not previously been investigated.

This does not mean that the IBS diagnosis is incorrect, but rather that it may not fully explain why symptoms are occurring.

Many patients go on to book consultations with us and test for SIBO. When the test is positive, we work with them to eradicate the overgrowth.

The Role of Gut Motility

The small intestine relies on a process called the migrating motor complex (MMC), which helps clear bacteria between meals.

When this process is disrupted for example, after food poisoning bacteria can accumulate.

This is one reason why SIBO often develops following gastrointestinal infections.

Signs Your IBS Might Actually Be SIBO

• Bloating after meals
• Symptoms triggered by carbohydrates
• Excess gas or belching
• Fatigue or brain fog
• Symptoms starting after infection
• IBS treatments not working

How to Get a SIBO Test in the UK

If you’ve been struggling with ongoing symptoms and not getting answers, testing may be a helpful next step.

A SIBO test can posted to do at home allowing you to complete the test at home and receive results within a few days.

If you suspect SIBO may be contributing to your symptoms, testing can provide valuable insight and help guide a more personalised approach.

Learn more about our SIBO Breath test
If you would like professional support, you can also book a consultation with our IBS specialists. For consultations visit our sister clinic ibs-solutions.co.uk-

Final Thoughts

Living with ongoing digestive symptoms can be frustrating, especially when you feel you haven’t been given clear answers.

For many people, the issue isn’t a lack of effort, but that the underlying cause hasn’t been fully explored.

If your symptoms are persistent or not improving, it may be worth considering whether something has been missed.

Related Articles

• Bloated even when not eating: what it could mean
• Does Candida cause bloating?
• IBS vs SIBO: how to tell the difference
• Foods to Avoid Hydrogen and Methane SIBO
• SIBO die-off explained
• Oregano oil for SIBO
• SIBO versus Candida
• SIBO and fat malabsorption

Frequently Asked Questions About SIBO

Can a GP test for SIBO in the UK?

In most cases, GPs cannot test for SIBO directly. Testing typically requires referral to a gastroenterologist, and availability varies depending on your local NHS trust. As a result, many patients are not routinely tested for SIBO within the NHS.

Why don’t doctors test for SIBO?

There are several reasons why doctors may not test for SIBO. These include limited access to testing, overlap of symptoms with IBS, time constraints in primary care, and the fact that SIBO testing is not part of standard IBS management guidelines.

Is SIBO recognised in the UK?

Yes, SIBO is recognised within gastroenterology. However, it is not routinely tested for in all NHS settings, which means many cases may go undiagnosed.

Why is SIBO often misdiagnosed as IBS?

SIBO and IBS share many of the same symptoms, including bloating, abdominal pain, and changes in bowel habits. Without specific testing, it can be difficult to distinguish between the two, which can lead to misdiagnosis.

How is SIBO diagnosed?

SIBO is most commonly diagnosed using a hydrogen and methane breath test. This involves drinking a sugar solution and measuring gas levels in the breath over time. Results are interpreted alongside symptoms and clinical history.

How accurate is SIBO testing?

Breath testing is widely used but not perfect. Results can be influenced by factors such as diet, gut transit time, and recent antibiotic use. This means false positives or false negatives can occur, so results should always be interpreted in context.

Can IBS actually be SIBO?

In some cases, yes. Research suggests that a proportion of people diagnosed with IBS may actually have underlying SIBO. This is one reason why symptoms may persist despite standard IBS treatment.

How can I get tested for SIBO in the UK?

You can access SIBO testing through:

• NHS referral (availability varies)
• Private testing (faster and more accessible)

Many private tests can be completed at home and provide quicker results.

What happens if SIBO is left untreated

If left untreated, SIBO may contribute to ongoing digestive symptoms, nutrient malabsorption, and reduced quality of life. In some cases, symptoms can persist or worsen over time.

Author – Victoria Tyler BSc Hons MBANT

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.

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.

References

Ghoshal, U.C., Shukla, R. and Ghoshal, U. (2017) ‘Small intestinal bacterial overgrowth and irritable bowel syndrome: A bridge between functional organic dichotomy’, Gut and Liver, 11(2), pp. 196–208.

Shah, S.C., Day, L.W., Somsouk, M. and Sewell, J.L. (2013) ‘Meta-analysis: antibiotic therapy for small intestinal bacterial overgrowth’, Alimentary Pharmacology & Therapeutics, 38(8), pp. 925–934.

Pimentel, M., Saad, R.J., Long, M.D. and Rao, S.S.C. (2020) ‘ACG clinical guideline: small intestinal bacterial overgrowth’, The American Journal of Gastroenterology, 115(2), pp. 165–178.

Rezaie, A., Buresi, M., Lembo, A. et al. (2017) ‘Hydrogen and methane-based breath testing in gastrointestinal disorders: The North American Consensus’, The American Journal of Gastroenterology, 112(5), pp. 775–784.

Ford, A.C., Lacy, B.E. and Talley, N.J. (2017) ‘Irritable bowel syndrome’, New England Journal of Medicine, 376, pp. 2566–2578.

National Institute for Health and Care Excellence (NICE) (2008, updated 2017) Irritable bowel syndrome in adults: diagnosis and management (CG61). Available at: https://www.nice.org.uk/guidance/cg61 (Accessed: 2026).

Quigley, E.M.M., Murray, J.A. and Pimentel, M. (2020) ‘AGA clinical practice update on small intestinal bacterial overgrowth: expert review’, Gastroenterology, 159(4), pp. 1526–1532.

Grace, E., Shaw, C., Whelan, K. and Andreyev, H.J.N. (2013) ‘Small intestinal bacterial overgrowth: prevalence, clinical features, current and developing diagnostic tests, and treatment’, Alimentary Pharmacology & Therapeutics, 38(7), pp. 674–688.