The aim of this research was to determine the dynamics of blood glucose concentration, liver and muscle of tilapia (Oreochromis niloticus), after food intake. The MSc. Leonel Aguilar Fiallos donated the tilapias. The experiment was performed at the Quinta Yolanda fish farm owned by the MSc. Aguilar located in Comarca Los Ranchos, Department of León, Nicaragua, Km 83 Highway to Managua, Motel La Gloria 400 meters to the east, 400 meters to the south. The organisms were kept in a concrete tank of 25 m3 until reaching an average weight of 90 ± 10gr. Subsequently, the tilapias were moved randomly to experimental tanks of 120 liters. A battery of 4 tanks was placed (1 control and 3 treatments of 2, 4 and 6 hours each), N = 10. Prior to the experiment, the tilapia were anesthetized, blood samples were taken, they were sacrificed and liver and muscle samples were taken. Subsequently, the samples were transferred to the Animal Physiology Laboratory for analysis. The results show that: in blood, glucose levels increase significantly at three hours, at six hours increases with respect to the group of three hours and prevails until nine hours. In muscle, the increase was observed at six hours and remained until nine hours. In liver, no significant differences were observed throughout the study period.