Diabetes is a growing problem in India, affecting all sections of the society and age groups. Diabetes mellitus is a heterogeneous group of metabolic disorders characterized by chronic hyperglycemia with disturbance of carbohydrate, fat and protein metabolism resulting from defects in insulin secretion, insulin action or both. A study was undertaken to estimate prevalence of hypomagnesaemia in patients with type 2 diabetes mellitus and to correlate the serum magnesium concentrations with micro- and macrovascular complications of diabetes - glycaemic control, retinopathy, nephropathy and neuropathy. Prevalence of hypomagnesaemia was significantly higher in patients with microvascular diabetic complications compared to diabetics with no complications. Hypomagnesemia was significantly associated with diabetic retinopathy and the studies undertaken illustrate that 'as the magnesium level decreases in type 2 diabetes mellitus patients, prevalence of retinopathy increases'. This book intends to raise attention to this issue among clinicians and public alike.