**6. Conclusion**

A two-way relationship between VD status and T1D and T2D can be argued. At the moment, it seems undeniable that there is a causal association between the risk of diabetes mellitus development and numerous polymorphisms in genes responsible for metabolism (CYP2R1 and CYP27B1) and signaling (VDR) of VD. Despite the fact that diabetes mellitus is a multifactorial disease, and it is unlikely that VD deficiency is the main cause of this pathology, there is no doubt that it may be used in the complex treatment of diabetes mellitus and its complications. The importance of more comprehensive and randomized clinical trials to determine the therapeutic role of vitamin D in preventing the progression of glucose intolerance in groups at high risk of developing T2D should be noted.
