Type 2 diabetes mellitus (T2DM) has reached epidemic proportions worldwide and animal models mimicking human T2DM are widely used to study mechanisms of disease and to develop pharmacotherapeutics. Over the last three decades, rodent models of T2DM have yielded more than 50 publications per month; however, many details of human T2DM pathogenesis remain unclear, and means of preventing disease progression remain elusive. This review investigates the reasons for this translational discrepancy by analyzing the experimental evidence from rodent models of T2DM. The analysis revealed significant species-specific differences at every level of glucose regulation, from gene/protein expression, cellular signaling, tissue and organ to whole organism level, when compared with data acquired using human cells, tissues, organs, and populations. Given the extensive species-specific barrier that creates an immutable translational gap, there is an urgent need to further employ and develop human-based research strategies to make significant strides against the current T2DM epidemic.