Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder. The most common symptoms of IBS are abdominal pain or discomfort, often reported as cramping, along with diarrhea, constipation, or both. IBS is diagnosed when a person has abdominal pain or discomfort at least three times per month for the last three months without other disease or injury that could explain the pain. The pain or discomfort of IBS may occur with a change in stool frequency or consistency or may be relieved by a bowel movement. IBS is often classified into four subtypes based on a person’s usual stool consistency: 1) IBS with constipation (IBS-C), 2) IBS with diarrhea (IBS-D), 3) Mixed IBS (IBS-M), and 4) Unsubtyped IBS (IBS-U).