Irritable bowel syndrome (IBS) is a common condition that causes recurring abdominal pain together with changes in bowel habit, such as diarrhoea, constipation or both. It does not damage the bowel, but it can affect daily life considerably.
Small intestinal bacterial overgrowth (SIBO) happens when too many bacteria grow in the small intestine. It can cause bloating, wind, diarrhoea and discomfort, and its symptoms overlap with IBS.
Ruling out other causes first
Because these symptoms are shared by other conditions, the first step is a careful history and examination. Depending on age and symptoms, tests may include blood tests, stool tests, a breath test for SIBO or lactose intolerance, and a colonoscopy or gastroscopy.
Warning signs that need prompt assessment
- Blood in the stool or black stools
- Unintended weight loss
- A change in bowel habit starting after about 50
- Anaemia, or a family history of bowel cancer or inflammatory bowel disease
Treatment
- Explaining what is happening in the gut, which itself often helps
- Diet changes, such as adjusting fibre or a supervised low-FODMAP diet
- Medicines targeted at the main symptom, such as pain, diarrhoea or constipation
- Antibiotics for confirmed SIBO
General information only. Reviewed by Dr Chia Chung King, 2026-11-07. Book a consultation.