There is accumulating evidence that the changes which occur in the metabolism of some micronutrients in diabetes mellitus might have a specific role in the pathogenesis and complications of this disease. Magnesium deficiency is the most evident disturbance of metal metabolism in insulin-dependent diabetes mellitus. Hypomagnesemia has been linked both to the acute metabolic and late chronic complication of diabetes. Of particular concern, is the association between hypomagnesemia and ischemic heart disease and severe retinopathy in humans with diabetes mellitus. Appropriate magnesium supplementation might prove beneficial in normalizing the low plasma and tissue magnesium levels and prevent or retard the development of vascular complications in diabetic patients. However, well designed and documented experiments need to be performed before the rationales for such therapy are well established.