Hydrogen (H₂) breath tests serve several purposes. (i) detect malabsorption of carbohydrates such as lactose and fructose, (ii) measurement of oro-caecal transit time (iii) associate hydrogen production with the onset of abdominal symptoms like bloating, flatulence, pain, and diarrhea (which indicates carbohydrate intolerance), and (iv) diagnose small intestinal bacterial overgrowth (SIBO). It is important to distinguish between carbohydrate intolerance and SIBO because their treatments differ significantly. Carbohydrate intolerance is typically managed through dietary restrictions, while SIBO requires antibiotic therapy. However, recent guidelines have questioned the accuracy of hydrogen breath tests in diagnosing SIBO due to variability in OCTT measurements. This limitation can be addressed by combining H₂ breath tests with imaging techniques such as scintigraphy, which independently confirm OCTT. When this combined approach is used, SIBO is diagnosed if the rise in breath H₂ occurs before the contrast agent appears in the large bowel. Despite its benefits, this combined method faces organizational and financial challenges that limit its routine clinical use. This retrospective cohort study aims to assess the clinical performance of a cheap and simple test that combines a 20g lactulose H₂ breath test with simple radiographic abdominal imaging to assess OCTT, SIBO, and carbohydrate tolerance. The novel innovation in this method is to confirm oro-caecal transit by taking an X-ray of the abdomen when H₂ production increases during the examination. If the contrast agent is not visible in the cecum when H₂ rises, this indicates the presence of SIBO. Conversely, if the contrast agent is present in the cecum at that time, it confirms normal OCTT, and any abdominal symptoms occurring after this point support a diagnosis of carbohydrate intolerance. If the method is proven to be valid, then this simple test will greatly facilitate the accurate diagnosis of SIBO and carbohydrate intolerance, allowing for more appropriate treatment decisions.