Abstract : This article presents a new formulation of insulin glargine concentrated at 300 U/mL (Gla-300). It is commercialized under the trade name of Toujeo® in an optimized pre-filled SoloStar™ pen for the treatment of type 1 and type 2 diabetes in adults. Besides a threefold higher concentration compared to the classical insulin Lantus® (100 U/mL or Gla-100), both pharmacokinetic and pharmacodynamic profiles of Gla-300 are flatter and longer (more than 24 hours) and have a lesser intra-/inter-variability, which makes them more reproducible. Overall, Toujeo® offers the same hypoglycaemic efficacy and the same safety profile when compared with Lantus®. However, a lower risk of hypoglycaemia, especially at night, a slightly smaller weight gain and a better flexibility in the time of injection have been reported. The two insulin formulations are not bioequivalent and the daily insulin requirement is slightly higher with insulin Gla-300 than with insulin Gla-100. The shift from an already available basal insulin towards Toujeo® may require a dose adjustment and a reinforcement of blood glucose monitoring.