What’s actually happening in the gut during an IBS flare-up?

IBS is classed as a functional bowel disorder, meaning the gut looks structurally normal but doesn’t work quite as it should. Many people with IBS have visceral sensitivity — their gut nerves are more responsive to stress than usual, so the gut-brain axis can become dysregulated. This means your gut may signal and respond to normal digestion in an exaggerated way, increase sensitivity to stretching or gas, while motility-related changes affect how quickly things move through your system.

What’s the difference between IBS-D, IBS-C, and IBS-M?

IBS is often subtyped based on your main symptom pattern. IBS-D is diarrhoea-predominant, IBS-C is constipation-predominant, and IBS-M (mixed-type) involves alternating between the two. Symptoms are frequently postprandial, meaning they flare after eating, and can be stress-induced — which is why IBS is sometimes wrongly dismissed as purely psychosomatic, when it’s a genuine physical condition with a strong gut-brain component.

What role does diet play, and what’s a low FODMAP diet?

Diet plays a major role for many people with IBS. A low FODMAP diet temporarily cuts out fermentable oligosaccharide, disaccharide, monosaccharide and polyol foods — the ones most likely to ferment in the gut and trigger symptoms — before gradually reintroducing them to identify your personal triggers. Getting the right balance of dietary fibre matters too: soluble fibre tends to be better tolerated than insoluble fibre if you’re dietary-sensitive, though everyone’s tolerance is different.

IBS: Your Complete Guide to Symptoms & Management

Irritable bowel syndrome is a common, long-term condition that affects the digestive system. It causes symptoms like stomach cramps, bloating, diarrhoea and constipation. While there is no single cure, understanding your specific IBS type and triggers is the first step to feeling better. With the right combination of diet changes, lifestyle adjustments and targeted medication, you can successfully manage your symptoms and improve your daily life.

Up to 1 in 5 people will experience irritable bowel syndrome at some point, making it one of the most common reasons patients speak to our virtual GPs. It is a genuine, recognised medical condition that occurs when the communication between your gut and brain becomes overly sensitive. Living with unpredictable digestion can feel incredibly disruptive, often affecting work, travel and social events. Modern management involves a tailored approach based on your specific symptoms, using trusted clinical strategies to help you regain control.

What is irritable bowel syndrome (IBS)?

Irritable bowel syndrome (IBS) is a common, long-term functional disorder that affects the large intestine and digestive system. According to the NHS, it causes symptoms such as stomach cramps, bloating, diarrhoea and constipation. Because it is a functional condition, the physical structure of the bowel appears normal, but it does not move as it should.

The gut-brain axis

To understand IBS, it helps to look at the gut-brain axis. This is a complex, two-way communication system between the enteric nervous system (often called the gut's "second brain") and your central nervous system. In IBS, this communication pathway is disrupted.

This disruption leads to two main issues. The first is visceral hypersensitivity, which means the nerves in the gut become exceptionally sensitive to normal stretch and pain signals. The second is dysmotility, where the muscles in the bowel wall change their speed. They might contract too quickly, causing urgency, or too slowly, causing backups.

Prevalence and demographics

IBS is very common. As outlined by the NICE guideline CG61, it affects between 10% and 20% of the general population in the UK. We know that it is particularly prevalent in women, who are significantly more likely to report symptoms than men. The condition typically begins in early adult life and usually starts before the age of 50. For many people, it is an intermittent condition, meaning symptoms can settle down for long periods before flaring up again, often with a significant impact on daily quality of life.

Main symptoms and when to see a doctor

The typical symptoms of IBS centre around abdominal discomfort and changes in how often or how easily you pass stool.

Common symptoms

The most frequent symptoms include:

Abdominal pain and cramping, which is often relieved or worsened by having a bowel movement.
Significant bloating of your stomach.
Excessive wind (flatulence).
Changes in your bowel habit, moving towards either diarrhoea, constipation, or alternating between the two.

The NHS notes that people with IBS also frequently report associated symptoms that are not strictly related to the bowel. These can include profound tiredness, feeling sick (nausea), backache, and problems passing urine.

Alarm symptoms

While IBS is uncomfortable, it does not cause physical damage to your bowel. However, certain symptoms are not typical of a functional disorder and require prompt medical investigation to rule out other, more serious conditions.

When to get urgent help

Call 999 if: you have severe, sudden, and unbearable stomach pain.

Call 111 or go to A&E if: you are unable to swallow, or you are vomiting blood.

You should book an appointment to speak with a GP as soon as possible if you experience any of these "red flag" symptoms:

Unexplained or unintentional weight loss.
Bleeding from your bottom or blood in your stool.
A hard lump or swelling in your stomach.
Shortness of breath, noticeable heart palpitations, or looking paler than usual (which could indicate anaemia).

These alarm features are carefully highlighted in NICE guideline CG61 as triggers for further investigation.

Types of IBS

IBS is categorised into distinct subtypes based on a person's predominant bowel habit, which dictates the most effective treatment approach.

Classification

In clinical practice, we do not treat IBS as a single, uniform condition. Instead, we classify it based on the primary way your bowel behaves when you are experiencing a flare-up. Clinicians use specific criteria, such as the Rome IV criteria, to determine your main symptom profile. Knowing your subtype is essential because a treatment that helps one type of IBS might actively worsen another.

Three main types

As set out in NICE recommendations, IBS is generally divided into three main categories based on stool consistency over time.

Type	Main Symptom	Stool Appearance	Primary Treatment Goal
IBS-C (Constipation)	Hard, infrequent stools	Lumpy, hard like nuts or sausage-shaped but cracked (Bristol Stool Chart types 1-2)	Increase moisture and motility
IBS-D (Diarrhoea)	Loose, watery, urgent stools	Fluffy pieces with ragged edges or entirely liquid (Bristol Stool Chart types 6-7)	Slow transit time and firm up stool
IBS-M (Mixed)	Alternating patterns	Fluctuates between hard lumps and liquid states	Stabilise bowel rhythm

Causes and triggers

The exact biological cause of IBS remains unknown, but it is generally understood to be a combination of physical, psychological, and microbial factors.

Causes

There is no single cause for irritable bowel syndrome. Instead, several mechanisms are thought to contribute. As discussed earlier, visceral hypersensitivity and problems with gut motility are central factors. Some people develop IBS shortly after a severe bout of gastroenteritis (a stomach bug), a condition known as post-infectious IBS.

There is also growing interest in the role of the gut microbiome, which is the complex community of bacteria living in your bowel. People with IBS often have a different balance of gut bacteria compared to those without the condition. Furthermore, some studies suggest a genetic component, as IBS can run in families, alongside evidence of low-grade, microscopic inflammation in the gut wall.

Personal triggers

While the underlying biological causes are complex, the day-to-day flare-ups are usually prompted by specific external triggers. Identifying these is a major part of managing the condition. According to the NHS, common triggers include:

Diet: Certain foods and drinks are notorious for aggravating a sensitive gut. These frequently include caffeine, alcohol, very fatty or spicy foods, and specific carbohydrates.
Stress and anxiety: The gut-brain axis means that emotional stress directly impacts bowel function. High anxiety periods almost always worsen IBS symptoms.
Hormonal changes: Many women notice their IBS symptoms fluctuate with their menstrual cycle, often becoming worse just before or during their period.

GP diagnosis

A GP diagnoses IBS primarily by taking a detailed clinical history of your symptoms and ruling out other conditions with simple tests.

GP appointments

Because there is no single definitive test for IBS, your consultation is the most important diagnostic tool. Our online GPs will ask you to describe your abdominal pain, your bowel habits, and any bloating. We will need to know exactly how long you have been experiencing these issues and whether they change after eating or opening your bowels. We will also ask directly about the "red flag" symptoms mentioned earlier to ensure a safe assessment.

Person sitting outdoors holding their stomach, marked as a featured article

Clinical criteria

Doctors look for a very specific pattern of symptoms over a set period. We follow the NICE recommendations to confirm a diagnosis. You might think of this as the "ABC" of symptoms: Abdominal pain, Bloating, and a Change in bowel habit.

A GP will consider an IBS diagnosis if you have had abdominal pain or discomfort that has been present for at least six months and is either relieved by opening your bowels or is associated with a change in bowel habit and is accompanied by at least two of the following symptoms: altered stool passage, abdominal bloating, passage of mucus or made worse by eating. This pattern gives us confidence that the issue is a functional one.

Ruling out other conditions

To ensure a high standard of care, as outlined by the NICE quality standard QS114, a GP will usually arrange a few basic investigations to exclude other problems.

They will typically request a blood test to check for coeliac disease, which is an autoimmune reaction to gluten that can mimic IBS. They might also request a stool sample to check for faecal calprotectin. This test looks for inflammation in the bowel, helping us differentiate IBS from inflammatory bowel disease. Unless you have alarm symptoms or abnormal test results, invasive procedures like a colonoscopy are not usually needed.

If you are unsure whether your symptoms are caused by a gluten issue or IBS, you can read more in our guide on coeliac disease versus gluten intolerance.

Managing IBS

Effective management of IBS relies on matching dietary changes, lifestyle adjustments, and medications to your specific subtype.

General lifestyle advice

Before looking at specific medications, there are foundational steps that benefit everyone with IBS. Regular physical exercise can improve bowel motility and reduce stress. Speaking of stress, techniques such as mindfulness, yoga, and ensuring adequate sleep are vital for calming the gut-brain axis. We also highly recommend keeping a food and symptom diary to help you and your clinician identify your personal triggers.

Managing IBS-D (Diarrhoea)

If you mainly struggle with loose stools and urgency, the goal is to slow down transit time.

Diet: The NICE guideline CG61 suggests focusing on soluble fibre, like oats, while cutting down on insoluble fibre found in bran and wholewheat. You should also limit caffeine and avoid sorbitol, an artificial sweetener found in sugar-free sweets that acts as a laxative.
Medication: The British National Formulary recommends antispasmodic medicines, such as peppermint oil or mebeverine, to help relieve stomach cramps. For short-term control of diarrhoea, loperamide can be very effective in slowing down the bowel.

Managing IBS-C (Constipation)

When hard, infrequent stools are the main problem, the focus shifts to softening the stool and encouraging movement.

Diet: You should gradually increase your intake of soluble fibre, drink plenty of water throughout the day, and consider incorporating foods like linseeds into your meals.
Medication: If diet is not enough, a GP can recommend laxatives. According to the British National Formulary, bulk-forming laxatives (like ispaghula husk) or osmotic laxatives (like macrogol) are preferred. Lactulose is generally avoided as it can worsen bloating and wind.

Advanced treatment options

When first-line treatments are not quite enough, there are second-line therapies available.

The Low FODMAP Diet: This involves temporarily eliminating specific fermentable carbohydrates that are poorly absorbed in the gut. The Cochrane Library notes evidence supporting its use, but it is a complex, restrictive diet. It is not meant to be followed forever and should always be undertaken with a trained dietitian.
Psychological Therapies: Because of the gut-brain connection, therapies like cognitive behavioural therapy (CBT) and gut-directed hypnotherapy are officially recommended by NICE for persistent IBS.
Medication: For long-term, difficult cramps , GPs sometimes prescribe very low doses of certain antidepressants. In this context, they are not used to treat depression, but to act as pain modulators, calming the sensitive nerve signals between the gut and the brain.

Living well with IBS

Taking proactive steps to track your symptoms and prepare for medical appointments can significantly improve your care experience.

Preparing for appointments

Consultations are most productive when you arrive with clear information. To get the most out of your time with a clinician, try to:

Track your symptoms for at least two weeks before you speak to us.
Write down a list of your key questions so you do not forget them.
Note any obvious triggers you have spotted.
Be ready to describe your stool consistency frankly. Looking at a copy of the Bristol Stool Chart beforehand can give you the right vocabulary to use.

Man holding both hands on his stomach, seated outdoors

Food and symptom diary

A symptom diary is a brilliant tool, but it needs to capture the right details. You should track everything you eat and drink, the exact symptoms you experience, and what time they occur. Crucially, you must also record your stress levels, sleep quality, and mood. The goal is not to diagnose yourself, but to find hidden patterns that you can share with a doctor or a registered dietitian.

Emotional and social impact

It is completely normal to feel anxious about socialising, working in an office, or travelling when you have an unpredictable bowel condition. The social isolation IBS can cause is significant. Simple planning, like checking restaurant menus in advance, mapping out toilet facilities on a journey, and carrying a small kit with wet wipes and antispasmodics, can help restore your confidence. If the psychological burden is feeling heavy, please read our broader guidance on managing stress and anxiety.

Conclusion

Irritable bowel syndrome is a real, complex gut-brain disorder, and it is certainly not "just in your head". Identifying whether you have IBS with constipation, diarrhoea, or a mixed pattern is the most vital first step toward getting the right help. From there, a tailored combination of dietary changes, lifestyle adjustments, and targeted medications forms a strong foundation for treatment. Finally, working alongside a doctor is essential to secure a correct diagnosis and safely rule out other underlying conditions.

While there is no single overnight cure for a sensitive gut, a systematic, patient-led approach can drastically improve your quality of life and help you feel in control again. If your digestion is disrupting your daily routine, our online GPs can assess your symptoms and help you build a personalised management plan. Book an appointment with Doctor Care Anywhere today to start taking control of your gut health.

The difference between IBS and IBD is that IBS is a functional disorder, whereas IBD is an autoimmune condition. According to the NHS, IBS involves a sensitive but physically healthy bowel with no visible inflammation. In contrast, inflammatory bowel disease (IBD) causes physical damage, ulcers, and active inflammation in the gut tissue, requiring completely different diagnostic tests and medical treatments.

Irritable bowel syndrome cannot lead to bowel cancer. According to the Royal College of General Practitioners, IBS does not cause any physical damage to the structure of the bowel. It does not increase your risk of developing bowel cancer, and it is not a life-threatening condition, even though the symptoms can be highly distressing.

To start a low FODMAP diet safely, you must always seek professional support and avoid attempting it alone. NICE recommendations advise undertaking this diet only with guidance from a healthcare professional, usually a registered dietitian. They ensure your meals remain nutritionally complete through the strict elimination phase, the gradual reintroduction phase, and your personalised diet plan.

Your IBS symptoms are worse during your period because hormonal fluctuations have a powerful effect on the digestive system. Changes in oestrogen and progesterone, alongside the release of prostaglandins that cause the uterus to contract, alter gut sensitivity and muscle motility. This explains why abdominal pain, bloating, and diarrhoea frequently worsen just before or during menstruation.

IBS is not a true food allergy, though it can involve food intolerances or sensitivities. A true food allergy triggers a systemic immune system reaction, which can be dangerous. Because IBS is a functional disorder, specific foods may cause digestive symptoms by fermenting in the gut or stimulating sensitive nerves, but they do not cause an immune response.

Irritable Bowel Syndrome (IBS): A Complete Guide