Abstract The main contribution of this work is to present a detailed scale-up procedure between human and rats models to more accurately predict what would happen in human beings, based on the experimental results obtained from rats. This procedure begins using the human model, given by Sorensen (1985). The proposed scale-up technique required to establish some assumptions, to do an intensive search in the literature about organs volumes and flow rates of body rats and a dedicated experimental work in the laboratory with these animals. Even though it is mainly focused on studying the endocrine system behavior to obtain a proper in in silico healthy rat it can be extended to study another body regions. Several simulation results with the obtained rat model are included and confronted with experimental data of ten healthy rats. The analogy between human and rat dynamic behavior after equivalent meal intakes are also discussed.