IBS is diagnosed clinically using the Rome IV criteria — recurrent abdominal pain at least one day per week for the last three months, associated with defecation, a change in stool frequency, or a change in stool appearance. It is divided into subtypes: IBS-C (constipation predominant), IBS-D (diarrhoea predominant), and IBS-M (mixed).
The gut–brain axis, intestinal motility, visceral hypersensitivity, and gut microbiome changes all appear to play a role; the mechanism varies between individuals.
Dietary management is central. The low-FODMAP diet, developed at Monash University, has the strongest evidence base — around 70% of people with IBS see meaningful symptom reduction. Stress management, regular meals, and adequate hydration also help. IBS shares some symptoms with IBD and other conditions; always discuss a new gut symptom with your clinician to ensure an appropriate diagnosis before self-managing with diet.