Summary: Nowadays 415 million people worldwide suffer from diabetes and many of them experience various gastrointestinal symptoms, such as abdominal pain, bloating or diarrhea. Here we want to discuss two out of its numerous potencial causes: exocrine pancreatic insufficiency and small intenstinal bacterial overgrowth (SIBO). Exocrine pancreatic insufficiency may result from diabetes, but it may also be its cause. It leads to malabsorption and, in consequence malnutrition, avitaminosis and microelements deficiency. Gold standard in assessing exocrine function of pancreas is secretin-cholecystokinin test. First- line treatment is pancreatic enzyme replacement therapy. Gut microbiota has many important functions in human organism. Pathological changes in its composition are called dysbiosis. SIBO is a specific type of dysbiosis. Among many causes contributing to SIBO, it is worth to notice gut motility disorders which often appear in diabetes (as a result of diabetic neuropathy) and which lead to slowing down food passage in bowel and intestinal bacterial overgrowth. Various antibiotics are used in the treatment of SIBO. Rifaximin, an eubiotic that is not absorbed from the bowel, deserves special attention. Its efficacy in restoring eubiosis (proper composition of gut microbiota) is proven, as well as its success in reducing body weight and improving glucose tolerance. Pre- and probiotics also play an essential role in the treatment of SIBO. Pancreatic exocrine insufficiency and SIBO may often coexist.