Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome (IBS) is a common, chronic disorder affecting the large intestine, characterized by recurrent abdominal pain along with a change in bowel habits — either constipation, diarrhea, or an alternating pattern of both. Unlike occasional constipation or diarrhea, IBS is a distinct, ongoing diagnosis with its own diagnostic criteria.

How IBS Is Diagnosed

There's no single test that confirms IBS. Instead, doctors use symptom-based criteria (commonly the Rome IV criteria): recurrent abdominal pain, on average at least one day per week over the past three months, associated with two or more of the following — pain related to bowel movements, a change in stool frequency, or a change in stool form. Other conditions with similar symptoms are typically ruled out first, especially if there are warning signs like blood in the stool, unexplained weight loss, or symptoms starting after age 50.

Subtypes of IBS

IBS is generally classified by the predominant bowel pattern: IBS-C (constipation-predominant), IBS-D (diarrhea-predominant), IBS-M (mixed, alternating between both), or IBS-U (unclassified, when symptoms don't fit clearly into the other three patterns).

How It Differs From Occasional Constipation

Our constipation guide covers the general causes and treatment of constipation, which is often temporary and related to diet, fluids, or activity. IBS is a distinct, chronic diagnosis — the abdominal pain component, its relationship to bowel movements, and its persistence over months are what separate it from a simple bout of constipation or diarrhea.

Our symptoms of IBS and treatment for IBS guides cover what living with and managing IBS actually involves.