C-peptide is secreted from proinsulin and over the recent decade is considered as an active peptide that leads to different capillary actions and macrovascular complications in patients with type 2 diabetes mellitus. Results of the recent researches showed the C-peptide uptake in the blood vessel walls, in the juxtaglomerular apparatus of malpighian tuft, induction of local inflammation, proliferative effect on mesangial cell. The given effects showed an atherogenic role of C-peptide. Authors consider C-peptide as a possible predicator of cardiovascular complications and mortality in patients with type 2 diabetes mellitus and without diabetes.