 There is increasing evidence that vitamin D affects the risk of diabetes. The role of vitamin D in type 2 diabetes is suggested by cross sectional studies, where an inverse association between vitamin D status and the development of type 2 diabetes has been found. Moreover supplementation with calcium and vitamin D may attenuate increases in glycemia and insulin resistance in healthy older adults with IFG. However further research is needed to confirm these findings and to determine possible mechanisms of the preventive effect from vitamin D against diabetes. The aim of this study is to examine the effect on metabolic parameters such as glycemic control, lipid status, inflammatory markers, insulin resistance and insulin secretion in patients with type 2 diabetes and vitamin D insufficiency before and after a 12-week period of treatment with high doses of vitamin D. 