INTRODUCTION: Several peptides are involved in the regulation of food intake and energy expenditure, among which are leptin, adiponectin, ghrelin and neuropeptide Y (NPY). These peptides may be implicated in the obesity seen in the majority of patients with type 2 diabetes mellitus (T2DM).AREAS COVERED: The present review considers: i) the role of leptin, adiponectin, ghrelin and NPY in patients with T2DM, and, ii) the effect of insulin as well as oral hypoglycemic, antihypertensive, hypolipidemic, antiobesity and antiplatelet agents on these peptides in patients with T2DM.EXPERT OPINION: Patients with T2DM have either lower or similar leptin levels, decreased adiponectin and ghrelin levels, and increased NPY circulating levels compared with nondiabetic controls. Treatment with insulin, oral hypoglycemic, antihypertensive, hypolipidemic, antiobesity and antiplatelet drugs may influence the levels of these peptides. It is not widely appreciated that several drugs commonly administered to patients with T2DM can influence adipokine levels. The clinical relevance of these effects needs to be evaluated.