The classic symptoms of irritable bowel syndrome (IBS) are abdominal pain, bloating and some form of bowel dysfunction. The pain is typically colicky in nature and can occur at any site although most commonly it is on the left side. The abdomen feels flat in the morning and then gradually becomes more bloated as the day progresses reaching a peak by late afternoon or evening. It then subsides again over night. Traditionally IBS is divided into diarrhoea, constipation or alternating subtypes. IBS patients frequently complain of one or more non-colonic symptoms, these include constant lethargy, low backache, nausea, bladder symptoms suggestive of an irritable bladder, chest pain and dyspareunia in women. The traditional view that IBS is a largely psychological condition is no longer tenable. Rectal bleeding, a family history of malignancy and a short history in IBS should always be treated with suspicion. Both pain and bowel dysfunction are often made worse by eating. It is recommended that a coeliac screening test is undertaken to rule out this condition. Other routine tests should include inflammatory markers such as CRP or ESR. Calprotectin is a marker for leukocytes in the stools and detects gastrointestinal inflammation. A negative test almost certainly rules out inflammatory bowel disease, especially in conjunction with a normal CRP. Fermentable carbohydrates can have a detrimental effect on IBS and this has led to the introduction of the low FODMAP diet.