Early detection of glycemic dysregulation and optimization of glycemic control in cystic fibrosis (CF) related diabetes (CFRD) is associated with improved pulmonary function and decreased mortality. The standard 2-hour oral glucose tolerance test (OGTT) is the current routine screening test for CFRD. However, hyperglycemia can be detected by continuous glucose monitoring systems (CGMS) in patients with normal OGTT evaluation. High-dose acarbose is an important alternative in the treatment of glycemic dysregulation especially accompanied by hypoglycemia. A 7-year-old boy with CF presented with hyperglycemia. Hypoglycemia (29 mg/dL) and hyperglycemia (400 mg/dL) were demonstrated by OGTT and intermittent CGM (iCGMS). Thickener was added to nutritional solutions and acarbose was initiated as 3x12.5 mg/dose and increased to 6x25 mg without any side effects. On the twentieth day of treatment, glycemic dysregulation resolved. In the early detection of CFRD, screening with OGTT after the age of 10 years may be inaccurate. Therefore, routine use of CGMS or iCGMS should be considered. In addition, in CFRD with severe hypoglycemia, acarbose may be an important alternative in the high and increased dose range.