What is IBS? Symptoms, Causes and Diagnosis

What is IBS?

IBS stands for irritable bowel syndrome. It is a chronic gastrointestinal disorder which presents with altered bowel habits; diarrhoea and/or constipation, abdominal pain and distention with no structural or biochemical abnormalities. IBS affects 10-20% of the population in the United Kingdom and is one of the most commonly diagnosed conditions by gastroenterologists. It is twice as common in women than in men 1 . However this could be due to men seeking advice less often than women regarding their gastrointestinal symptoms. The true prevalence may be higher, as is it thought that only a 1/3 of IBS cases are diagnosed 2

There are four types of IBS:

  1. Diarrhoea predominant IBS (IBS-D).  >25% of bowel movements type 6-7.
  2. Constipation predominant IBS (IBS-C)  >25% of bowel movements types 1-2 .
  3. Mixed/alternating IBS (IBS-M). This is were the symptoms alternate between diarrhoea and constipation.
  4. Unclassified (IBS-U)

The main clinical symptoms include: 1

  • diarrhoea and/or constipation
  • abdominal pain or discomfort
  • bloating
  • excessive flatulence

Look at the Bristol Stool Chart below to help identify your stool consistency. Type 1-2 indicate constipation and 6-7 indicate loose stools.

Symptom severity does differ between individuals with IBS and also within the individual over time.  The following changes may be noticed:

  • symptom severity can change
  • new symptoms may emerge
  • bowel habit may alternate between constipation and diarrhoea
  • symptoms may resolve for a period and then return3.

These fluctuations can leave IBS sufferers feeling frustrated, anxious and distressed. This can have a huge impact on quality of life. 

What causes IBS?

The cause is still unknown however it is thought that it is multi-factorial. Some proposed theories include altered gut motility, enhanced gut-brain communication, visceral hypersensitivity, altered gut microbiota and genetics. Low grade inflammation and immune alterations for example as a result of gastroenteritis may also play a role.  

How is IBS diagnosed? 1

IBS should be diagnosed by a doctor or gastroenterologist using the Rome IV criteria and by undertaking a detailed history. IBS diagnosis is considered if the individual has recurrent abdominal pain at least 1 day a week for the past 3 months that is associated with 2 or more of the following: 3

  • related to defecation
  • associated with a change in a frequency of stool
  • associated with a change in form (consistency) of stool

The doctor should also look out for possible red flags as IBS symptoms do overlap with those of other diseases. Alarm features to look out for include:

  • unexplained weight loss
  • family history of bowel disease
  • onset of symptoms after the age of 50
  • blood in the stool
  • anaemia
  • persistent daily diarrhoea
  • fever
  • getting up at night to open your bowels
  • recurrent vomiting

If you are experiencing any of the above please see your doctor.

A series of investigations is usually carried out prior to diagnosis. This includes a blood test including: 3

  • a full blood count (FBC)
  • erythrocyte sedimentation rate (ESR) or plasma viscosity **
  • c-reactive protein (CRP) **
  • antibody testing for coeliac disease.

**The ESR and CRP tests are conducted to detect inflammation in the body which can be caused by disease such as inflammatory bowel disease. Sometimes a stool sample is requested to test for faecal calprotectin which also looks for the presence of inflammation. 

All these are important to prevent misdiagnosis. Other tests may be carried out but these may not be necessary to confirm diagnosis. 3

Is there a cure?

Unfortunately no. Medication, diet, supplements, lifestyle changes and psychological therapies can be used for optimal symptom control.

Watch out for future posts on dietary strategies for the management of IBS.


  1. NICE CG61, 2015. Irritable bowel syndrome in adults: diagnosis and management of irritable bowel syndrome in primary care. Available at https://www.nice.org.uk/guidance/cg61/resources/guidance-irritable-bowel-syndrome-in-adults-diagnosis-and-management-of-irritable-bowel-syndrome-in-primary-care-pdf
  2. Hungin AP, Whorwell PJ, Tack J, et al. The prevalence, patterns and impact of irritable bowel syndrome: an international survey of 40,000 subjects. Aliment Pharmacol Ther 2003;17:643-50.
  3. El-Serag HB, Pilgrim P, Schoenfeld P. Systemic review: Natural history of irritable bowel syndrome. Aliment Pharmacol Ther 2004;19:861-70.

Updated in August 2020

6 thoughts on “What is IBS? Symptoms, Causes and Diagnosis

  1. Thanks for caring about the IBS community, MEVSIBS.

    I find that whole grains (insoluble) are problematic whenever I experience a flare-up. I increase my soluble fiber with foods like cooked fruits (skins removed) and Benefibre. Low FODMAP didn’t work for me, but everyone is different.

    Liked by 1 person

    1. You’re most welcome Kathy. As an IBS sufferer myself I know how difficult dealing with IBS can be. You are very right everyone with IBS is very different from the symptoms experienced, their severity and responses to treatment. All this makes it that much harder to treat. When it comes to the low FODMAP diet it only works for approximately 70% of patients. I am sorry to hear it did not work for you but it looks like you have identified other common dietary triggers. Recent research has found that gut directed hypnotherapy is as effective as the low FODMAP diet. It may be something worth considering if your symptoms are still impacting on your daily activities.


        1. Aargh. Typo.

          Sadly, like the low-FODMAP approach, self-hypnosis doesn’t work for everyone.

          Sometimes fingers work faster than brains. 😉 Too bad we can’t control our IBS symptoms like we can edit with a word processor. “Ooooh. That food didn’t agree with me.” *Back to beginning of day, edit out offending food, and insert changed results.*

          Come to think of it, maybe time travel is the answer. Go back. Fix. SMILE.


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