Summary: Small intestine bacterial overgrowth (SIBO) is a clinical syndrome caused by bacterial overgrowth in the lumen of the small intestine. It develops in the course of chronic diseases such as irritable bowel syndrome, inflammatory bowel disease, diabetic neuropathy, cirrhosis, it may occur with long-term proton pump inhibitor (PPI) therapy. SIBO is diagnosed in approximately 70% of patients taking PPI for more than one year. In SIBO diagnostics, hydrogen breath tests (HBT) are used, during which the hydrogen concentration in the patient's exhaled air is measured after lactulose or glucose intake. The most common symptoms of the disease include abdominal pain and discomfort, flatulence, a feeling of postprandial fullness, excessive gas and diarrhea. Rifaximin and other broad-spectrum antibiotics with a low-FODMAP diet are used in the treatment.