Is it IBS or something else?

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Learning objectives

After reading this feature you should be able to:

• Understand why IBS can occur
• Be able to recommend suitable treatments and self-care strategies to patients
• Know which symptoms are red flags and/or require further investigation to rule out conditions such as irritable bowel disease.

Key facts

• IBS is extremely common in the UK, but it often goes undiagnosed or misdiagnosed
• There is usually no specific cause, but stress, anxiety and food can trigger flare-ups 
• Diagnosis is vital for correct management and to rule out other conditions with similar symptoms.

According to the charity Guts UK, irritable bowel syndrome (IBS) is one of the most common reasons why people visit their GP, with as many as one in eight adults experiencing symptoms at any one time. 

IBS is usually diagnosed in people aged 20-39 years and in more women than men, becoming less common as people get older. It is believed to be a disorder of gut-brain function, related to an oversensitive digestive system, abnormal immune system activity and/or changes in the gut microbiome. There is generally no specific cause, but IBS sometimes develops after an infection or a course of antibiotics. Stress, anxiety and certain foods may worsen the symptoms.

While IBS symptoms can often be managed with lifestyle changes and medicines, diagnosis is a significant challenge. There is no definitive test, so ruling out other bowel conditions first is essential. Unfortunately, many people are self-diagnosing and self-managing their symptoms with OTC medicines rather than seeking advice from a healthcare professional. 

There are concerns that doing so may be masking more serious bowel conditions, such as coeliac disease and inflammatory bowel disease (IBD). “Survey data suggests that some people with bowel symptoms can wait up to six months before seeing their GP,” says Julie Thompson, Guts UK information manager. 

If these patients do present in pharmacy, Thompson says: “It would be helpful to discuss their situation in a more private area of the pharmacy. They can try some medicines while they wait for a GP appointment – for example, OTC laxatives and antispasmodics. Antidiarrhoeal medicines could also be trialled, unless the person goes on to develop any red flag symptoms, such as blood in stools or an associated fever.”

The National Primary Care Diagnostic Pathway for Lower Gastrointestinal (GI) Symptoms was launched in July 2024, alongside the website What’s Up With My Gut? Both are endorsed by various organisations, including the Royal Pharmaceutical Society (RPS). 

The aim is to provide support to GPs and other first-contact healthcare professionals such as pharmacists, while making the diagnosis process easier to understand for patients.

Identifying symptoms

IBS causes a range of digestion-related symptoms, many of which overlap with other bowel conditions. The most common IBS symptoms are abdominal pain, cramps or discomfort, abnormal bowel habits, wind and bloating, nausea, and mucus in the stools. 

One-third of people with IBS suffer from bouts of constipation (IBS-C), one-third suffer from bouts of diarrhoea (IBS-D) and one-third suffer from a mixture of the two (IBS-M). If people develop IBS after gastroenteritis (post-infectious IBS), they are most likely to have IBS-D. 

“IBS is a syndrome, or collection of symptoms, which means symptoms external to the bowel can occur,” says Thompson. “More general symptoms of IBS can include feeling tired or sick, backache and bladder problems. Identifying the different types of IBS is important because treatments often work quite differently. However, the pattern of bowel movements can alter over time, which means that treatment for those with IBS might need to change should their symptoms vary.”

In some people, IBS symptoms can be severe enough to require specialist treatments. 

“Because irritable bowel syndrome is often the diagnosis made when all other possibilities for the gastrointestinal issues have been excluded, it is easy to consider it a minor condition,” says Emma Murray, a locum pharmacist in Norfolk and lead pharmacist at digital healthcare provider Evaro.

“The reality is that it can have a significant impact on people’s daily lives and wellbeing. Therefore anyone affected should be encouraged to seek advice from a healthcare practitioner and try to develop a management plan that works for them.”

Differential diagnosis

It is important that people discuss all of their bowel symptoms, even if they flare up and down or if some symptoms are worse than others. This symptom pattern is common not only with IBS, but with many other bowel conditions. 

It is particularly important to see a GP about changes in bowel habits lasting for four weeks or more, as well as rectal bleeding or anaemia, a noticeable lump in the abdomen, waking up from sleep to empty the bowel, unintentional weight loss, a fever and ongoing fatigue – especially in those over 50 years of age or with a family history of bowel disease, including cancer. 

IBS should not be diagnosed on symptoms alone. British Society of Gastroenterology (BSG) guidelines on diagnosing and managing IBS in primary and secondary care recommend that everyone who consults their GP about IBS for the first time should be offered blood tests, including C-reactive protein or erythrocyte sedimentation rate, to test for inflammation and key markers for coeliac disease. 

People under 45 years of age with diarrhoea should be tested for faecal calprotectin to exclude inflammatory bowel disease, and GPs need to follow local and national guidelines for bowel cancer screening. Women aged 50 years or over with new IBS symptoms in the previous 12 months should be investigated to rule out ovarian cancer.

As long as there are no red flag symptoms, and blood tests and stool tests are normal, a GP can make a positive diagnosis of IBS. If the diagnosis remains unclear, a GP is likely to refer patients to a gastroenterologist, who may suggest a colonoscopy.

Bowel conditions that cause some similar symptoms to IBS include Crohn’s disease, ulcerative colitis, coeliac disease, bowel cancer, small intestinal bacterial overgrowth (SIBO) and infections such as giardiasis. It is possible to develop these conditions alongside IBS, which is why it is important that people seek medical advice if their IBS symptoms change or worsen. 

“Temporary gastrointestinal symptoms can come and go for lots of non-chronic reasons – infection, stress or change in diet, for example,” says Pearl Avery, IBD nursing lead for Crohn’s & Colitis UK. “So if OTC treatments for IBS are to be used, this should only be in the short term. If symptoms persist, patients should go to see their primary care practitioner. 

“It isn’t possible to tell the difference on symptoms alone, so sufferers should always consider further tests, even if these have been done in the past. There is no age cut-off for developing GI conditions, so these should always be a consideration in differential diagnoses.”

NICE Guideline NG20 for the Recognition, Assessment and Management of Coeliac Disease recommends that a diagnosis of IBS must not be made without first ruling out coeliac disease. People with symptoms can visit the ‘Is it coeliac disease?’ website (isitcoeliacdisease.org.uk) to determine if they should be tested.

“Sadly, one in four people diagnosed with coeliac disease have previously been treated for or misdiagnosed with IBS,” say Coeliac UK director of evidence and policy Heidi Urwin and consultant gastroenterologist Professor David Sanders. “Coeliac disease is estimated to affect one in 100 people, yet only 36 per cent currently have a medical diagnosis. It can take on average 13 years from onset of symptoms for an adult to gain a diagnosis of coeliac disease. 

“If someone is having a coeliac screen, they should be advised not to eliminate or reduce gluten from their diet. They need to include gluten in more than one meal per day, every day for six weeks, to prevent a false negative result.”

IBS management 

Once a person has been diagnosed with IBS, they may be able to manage their symptoms with lifestyle changes and self-help measures. 

According to BSG guidelines, everyone with IBS should be advised to take regular exercise. Soluble fibre (such as oats or ispaghula) can be an effective treatment for IBS pain and other symptoms, but insoluble fibre (wheatbran) should be avoided as it can make symptoms worse. It is important to build up intake of soluble fibre gradually to avoid bloating. 

Up to 90 per cent of people report that certain foods trigger their IBS symptoms, with common culprits including alcohol, caffeine, and spicy and fatty foods. Avoiding triggers is important, but people should consult a dietitian to avoid unnecessary exclusions or nutritional deficiencies. A gluten-free or low gluten diet is not usually recommended for IBS, although some people find it helps. 

A FODMAP diet (low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols) may ease IBS symptoms, but this should be supervised by a trained dietitian. 

Research shows that probiotics may help in IBS, but there are no recommendations or guidelines on a specific species or strain. “Probiotics may be effective for global symptoms and abdominal pain,” says Julie Thompson. “As the gut microbiome composition varies individually, probiotics may not work for everyone. 

“Any product should have some evidence that it is effective for IBS and be tried for up to 12 weeks. If it is effective it should be continued, as there is inadequate evidence to suggest that probiotic microbes repopulate the gut.”

The BSG guidelines say the most appropriate over-the-counter medicines for IBS depend on the predominant symptoms. 

Options include polyethylene glycol for constipation and loperamide for diarrhoea. “Smooth muscle relaxants can be tried to reduce abdominal pain – for example, mebeverine hydrochloride or alverine citrate,” says Thompson. “This also includes peppermint oil capsules, but these should be avoided if the patient also has gastro-oesophageal reflux disease (GORD). People with the mixed stool form (constipation and diarrhoea) may benefit from a bulking laxative – for example, ispaghula, sterculia or psyllium.”

If pharmacy medicines fail to work, a GP may prescribe tricyclic antidepressants or selective serotonin reuptake inhibitors, which reduce nerve sensitivity. Other prescribed medicines for IBS symptoms are available in secondary care, following further assessment and investigations. 

Psychological therapies, such as IBS-specific cognitive behavioural therapy and gut-directed hypnotherapy, are recommended if IBS symptoms have not responded to medicines after 12 months. However, they can also be used earlier on in IBS management.

Severe or treatment-resistant IBS needs a multidisciplinary treatment approach. For most people, a combination of lifestyle changes, medicines and psychological therapies should help to improve their symptoms and quality of life. However, it is important that pharmacists can discuss the limitations of all available treatments since IBS is unlikely to be completely cured.