Both hypertension and type 2 diabetes mellitus are common and there are no reliable markers either to predict their development or complications. High fat diet and carbohydrate-rich diet enhance serum asymmetrical dimethylarginine (ADMA) levels, an endogenous inhibitor of nitric oxide synthesis. ADMA levels are elevated in patients with hypertension, poor control of hyperglycemia, diabetic microangiopathy and macroangiopathy and dyslipidemia. One of the earliest signs of vascular dysfunction and insulin resistance, which are present in hypertension and type 2 diabetes mellitus, is an elevation in serum ADMA levels. Displacing plasma ADMA by oral supplementation of L-arginine restores endothelial dysfunction by augmenting endothelial nitric oxide generation. Strict control of hyperglycemia decreases serum ADMA levels. These and other studies suggest that serum ADMA levels could be used to predict the development of hypertension and type 2 diabetes mellitus in those who are at high-risk to develop these diseases.