SIBO and Ulcerative Colitis share many symptoms, making diagnosis challenging. Hydrogen breath testing is the gold standard for SIBO, but it’s rarely offered on the NHS. IBS Clinics provides private testing and tailored support to identify underlying causes and create effective treatment plans for lasting relief.
Living with Ulcerative Colitis can already bring a host of digestive challenges. When gas, bloating, or unexplained abdominal discomfort appear on top, Small Intestinal Bacterial Overgrowth (SIBO) may be part of the picture. Although SIBO and Ulcerative Colitis are separate conditions, their symptoms can overlap, making it difficult to tell where one ends and the other begins.
Accurate diagnosis is key, yet this is often easier said than done. Many patients find that standard NHS pathways don’t routinely include SIBO testing, leaving them to manage symptoms without a clear understanding of the cause. In clinical practice, the hydrogen breath test is the gold standard for identifying SIBO, while methods such as jejunal aspirate are rarely used and imaging is not a valid diagnostic tool.
In this article, we’ll explore the possible connection between SIBO and Ulcerative Colitis, look at how SIBO is diagnosed and treated (see our article on Berberine and SIBO for more on natural remedies), and discuss why private testing, nutritional support, and advice on how to treat SIBO at home, may provide a more complete path towards relief.
Understanding SIBO and Ulcerative Colitis
What is Small Intestinal Bacterial Overgrowth (SIBO)?
SIBO occurs when excessive amounts (or the wrong kind) of bacteria grow in the small intestine – an area of the gut that normally contains relatively low levels of bacteria compared to the large intestine. This overgrowth can interfere with digestion and nutrient absorption, leading to symptoms such as bloating, abdominal pain, diarrhoea, constipation, and excessive gas [1].
Because these symptoms are common in several digestive conditions, including Irritable Bowel Syndrome (IBS) and Ulcerative Colitis [1], SIBO can often go undiagnosed without specific testing. Left untreated, as well as causing ongoing digestive discomfort, SIBO can also contribute to nutritional deficiencies, fatigue, and the development of other health conditions including kidney stones and osteoporosis [2].
How Ulcerative Colitis affects the digestive system
Ulcerative Colitis (UC) is a type of Inflammatory Bowel Disease (IBD) that causes chronic inflammation and ulcers in the lining of the colon and rectum. This inflammation disrupts the normal function of the bowel, leading to symptoms such as diarrhoea, urgency, abdominal cramping, and rectal bleeding [3].
The ongoing inflammation and changes in bowel function seen in Ulcerative Colitis can sometimes create an environment that makes bacterial imbalances, including SIBO, more likely. This overlap of symptoms can make it difficult to know whether bloating or discomfort is linked to UC itself, a flare-up, or the presence of SIBO.
Can SIBO and Ulcerative Colitis Be Linked?
Why people with Ulcerative Colitis may be more prone to SIBO
Research suggests that people with Ulcerative Colitis may have a higher risk of developing SIBO [4]. This is partly because chronic inflammation can disrupt the normal balance of bacteria in the small intestine [4]. The use of certain medications, such as steroids or immunosuppressants, can also affect gut microbiota, making bacterial overgrowth more likely. In addition, previous surgeries or structural changes in the digestive tract may create conditions that encourage bacterial build-up in the small intestine [2].
Overlapping symptoms that can complicate diagnosis
Both SIBO and Ulcerative Colitis share a number of symptoms, including bloating, abdominal pain, diarrhoea, and changes in bowel habits [1]. This overlap can make it difficult for patients and even healthcare providers to distinguish between a UC flare-up and the presence of SIBO [2]. As a result, SIBO may remain undetected in people with Ulcerative Colitis, leaving them to continue managing symptoms without fully addressing one of the potential underlying causes. Accurate testing is therefore essential in determining whether SIBO is contributing to ongoing digestive discomfort.
How SIBO Is Diagnosed in Clinical Practice
For people living with Ulcerative Colitis, distinguishing between a flare-up and the presence of SIBO is essential. Treating SIBO without a confirmed diagnosis risks unnecessary antibiotic use, while ignoring it could mean ongoing symptoms such as bloating, abdominal pain, and diarrhoea remain unresolved. Accurate testing helps identify whether SIBO is contributing to discomfort and ensures that treatment is both targeted and effective.
Hydrogen breath testing as the gold standard
In clinical practice, the hydrogen breath test is considered the gold standard for diagnosing SIBO [5]. It works by measuring the levels of hydrogen and methane gases you exhale after drinking a sugar solution, such as lactulose or glucose. If bacteria are overgrowing in the small intestine, they ferment the sugar, producing measurable gases that are not typically present in large amounts at that stage of digestion. The test is simple, non-invasive, and widely available privately, including at IBS Clinics, making it the preferred diagnostic method for most clinicians.
Why jejunal aspirate is rarely performed in practice
Although jejunal aspirate – a procedure where fluid is taken directly from the small intestine and cultured for bacteria – is sometimes described in theory as the most accurate test, it is rarely performed in practice. It requires a hospital-based endoscopy, is invasive, and not routinely offered outside specialist settings. Most clinicians and patients find it impractical compared to breath testing and is no longer recommended [5].
Imaging studies – why they don’t diagnose SIBO
While imaging techniques such as CT or MRI scans can be useful in assessing structural changes in the digestive tract, they cannot diagnose SIBO. As this test does not measure bacterial activity or fermentation in the small intestine, it cannot confirm SIBO as a cause of symptoms, though can be useful in determining whether structural abnormalities may be causing the SIBO [5].
Limitations of Diagnosis in NHS Clinical Practice
Current NHS diagnostic pathways, such as NICE Clinical Guideline CG61 for Irritable Bowel Syndrome, explicitly indicate that hydrogen breath testing (for lactose intolerance and bacterial overgrowth) is not necessary to confirm an IBS diagnosis in people who meet the criteria [6]. As a result, GPs typically focus on standard blood and stool tests and symptom-based IBS management rather than testing for SIBO.
What this means for patients seeking answers
The absence of routine SIBO testing on the NHS can lead patients to endure unresolved symptoms and rely on dietary trial and error or symptomatic management. This is why many choose to seek private hydrogen breath testing, which provides timely, accurate diagnosis and allows for targeted treatment planning.
How IBS Clinics Can Help
At IBS Clinics, we offer hydrogen breath testing as part of our comprehensive approach to digestive health. Unlike the NHS, where this test is not routinely available, our service ensures you can access accurate testing without long delays or unnecessary referrals.
What makes our approach different
We don’t stop at simply providing a test. Alongside your hydrogen breath test, our practitioners review your full health history, current symptoms, and dietary patterns. This allows us to place your results in context and recommend a personalised plan rather than offering a one-size-fits-all solution. You can even subscribe to our unique course that guides you on how to manage SIBO at home.
Early and accurate diagnosis can make all the difference. By identifying whether SIBO is contributing to your symptoms, we can guide you toward the most appropriate treatments and nutritional strategies. This not only helps reduce bloating, gas, and discomfort more effectively, but also prevents the frustration of trial-and-error approaches that don’t address the underlying cause.
Treatment Options for SIBO with Ulcerative Colitis
Antibiotics are often used to treat SIBO by reducing bacterial overgrowth in the small intestine [5]. For patients with Ulcerative Colitis, antibiotic therapy must be carefully considered, as altering the gut microbiome can sometimes influence UC activity and cause bacterial resistance [5]. Treatment is typically guided by test results and overseen by a healthcare professional to ensure safety and effectiveness.
Nutritional strategies and probiotics for reducing symptoms
Alongside medical treatment, nutrition plays a central role in managing both SIBO and Ulcerative Colitis [5]. Adjusting the diet to limit fermentable carbohydrates (often called a low-FODMAP approach) may help reduce bloating and gas. Probiotics may also be recommended in some cases to support a healthier gut microbiome, though the choice of strain and timing should be tailored to the individual. Because UC and SIBO symptoms can overlap, personalised guidance is far more effective than general advice or restrictive trial-and-error diets.
Supporting gut health while managing Ulcerative Colitis
Self-treatment may offer temporary relief, but without proper diagnosis and monitoring, symptoms can persist or even worsen. With the right professional guidance, you can manage both SIBO and Ulcerative Colitis more effectively and improve your quality of life.
Managing SIBO in the context of Ulcerative Colitis requires a careful balance. The goal is not just to reduce bacterial overgrowth, but to maintain remission of UC and protect long-term gut health. This may involve a combination of targeted antibiotics, dietary adjustments, and nutritional support to ensure the digestive system has the resources it needs to heal and function effectively.
A functional medicine approach goes beyond symptom control, aiming to restore microbial balance and support gut healing. This may include structured dietary adjustments, targeted probiotics, and guidance on lifestyle changes that promote long-term digestive health. Regular monitoring and collaboration with your gastroenterologist or functional medicine practitioner can help keep both conditions under control.
By addressing the underlying causes of bloating, gas, and discomfort, our practitioners help you take practical steps towards lasting relief and improved gut health, even when Ulcerative Colitis complicates the picture.
Conclusion
SIBO and Ulcerative Colitis can be challenging to manage, especially when their symptoms overlap. While NHS care provides essential support for Ulcerative Colitis, SIBO testing is rarely available, leaving many patients without clear answers. At IBS Clinics, we offer hydrogen breath testing alongside tailored nutritional and functional medicine support to help identify the root causes of your digestive symptoms and create a plan that works for you.
If you’re ready to take control of your gut health and find lasting relief, we’re here to help. Contact us at IBS Clinics today to arrange your consultation.
References
- https://my.clevelandclinic.org/health/diseases/21820-small-intestinal-bacterial-overgrowth-sibo
- https://www.mayoclinic.org/diseases-conditions/small-intestinal-bacterial-overgrowth/symptoms-causes/syc-20370168
- https://www.nhs.uk/conditions/ulcerative-colitis/
- Yang C, Guo X, Wang J, Fan H, Huo X, Dong L, Duan Z. Relationship between Small Intestinal Bacterial Overgrowth and Peripheral Blood ET, TLR2 and TLR4 in Ulcerative Colitis. J Coll Physicians Surg Pak. 2020 Mar;30(3):245-249. doi: 10.29271/jcpsp.2020.03.245. PMID: 32169129. Available at: https://pubmed.ncbi.nlm.nih.gov/32169129/
- https://www.mayoclinic.org/diseases-conditions/small-intestinal-bacterial-overgrowth/diagnosis-treatment/drc-20370172
- https://www.nice.org.uk/guidance/cg61/resources/irritable-bowel-syndrome-in-adults-diagnosis-and-management-pdf-975562917829
Author – Tracey Randell
At IBS Clinics, Tracey Randell, a renowned Nutritional Therapist and one of the few IFM Certified Practitioners in the UK, extends her specialised knowledge and unique approach to managing and treating IBS and other gut-related conditions effectively.
Tracey’s profound understanding of Functional Medicine allows her to connect the dots for complex health conditions, identifying and addressing the root causes to curate personalised and comprehensive health plans for her patients. Her holistic approach focuses on resolving underlying imbalances and optimising gut health, enabling the body to correct other issues and attain overall well-being.
At IBS Clinics, we are dedicated to being your partner in navigating your gut-related health concerns, offering expert care and individualised treatment plans to alleviate your IBS symptoms and enhance your quality of life.
You can read more about Tracey on our About page here.
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