There is a body of evidence in Type 1 and Type 2 Diabetes that “resting” the pancreas by giving insulin in the early stages of the disease allows the pancreatic beta cells to recover, thereby delaying progression of disease. This has not been looked at in CF and our study aims to test this. Hence, the main objective of this study is to test the folowing hypothesis: Supplementation with small doses of insulin in individuals with CF and altered glucose tolerance leads to an improvement in the first phase responses in beta-cell functioning