Type 2 diabetes mellitus is a progressive disease characterised by a steady loss of beta cell function and an increase in the proinsulin/insulin ratio. During the recent years intact proinsulin has been the topic of interest in numerous preclinical and clinical studies in patients with type 2 diabetes mellitus. Intact proinsulin was confirmed as a marker of functional beta cell failure and as a predictor of increased beta cell loss due to apoptosis and/or diminished neogenesis.