Neonatal nutrition is an important subject in health in the short, medium and long term. In preterm newborns, nutrition assumes a predominant role for the child´s overall development. Babies with uncoordinated swallowing or respiration may not have the necessary oral abilities to suck the mother´s breast and will need to implement diferent feeding practices; one of them is changing the consistency of the milk offered. Objectives: Determine viscosity variations of untreated human and pasteurized milk without and with thickening to adapt the diet to the needs of dysphagic infants hospitalized in the Neonatal Intensive Cara Unit (NICU). Material and Methods: The authors altered the viscosity of natural infants powdered milk and, after thickening, determined and adopted a thickened in concentrations of 2%, 3%, 5% and 7% the viscosity were determined every 20 minutes for a period of 60 minutes at a temperature of 37ºC. Results: The infant lactose formula thickened at concentrations of 2% and 3% produced viscosities of 8.97cP and 27.73 cP, respectively. The increases were significantly different after 1 hour. Inversely, untreated human milk at 2%, 3%, 5% and 7% produced diminished viscosity over time; the changes were more accentuated in the first 20 minutes. In pasteurized human milk, the 2% concentration had no variation in viscosity, but with the 3%, 5% and 7% concentration, there was a significant decrease in the first 20 minutes with stability observed in the subsequent times. Conclusion: In powdered milk, the viscosity increases over time: the viscosity in human milk diminishes. The results point out the importance not only of considering the concentration of the thickener but also the time being administered after its addition to effectively treat dysphagic infants.