OBJECTIVES To determine the less costly alternative of parenteral nutrition in Public Health Care Institutions in Mexico. METHODS A cost-minimization study was performed comparing the use of RTU (considering four different formulations with 3.6g, 6.6g, 11.2g and 13.2g of nitrogen) against equivalent CNF preparations made by a third-part company. This study compared all direct and indirect costs considering an institutional perspective based on data collected from the main Public Health Institution in Mexico. Costs associated with third-part services were estimated within a Monte Carlo Simulation. Costs of the equivalent RTU TPN bags were obtained from a manufacturer. Results were evaluated with a Student t-test considering the mean use of 20 bags a day in order to evaluate if there is any significant differences between the costs of in-hospital and third-part companies preparations for long-term use of TPN. RESULTS Third-part services costs showed a triangular distribution according to Monte Carlo results. RTU costs were 9.95%, 16.93%, 36.45% and 27.21% lower than CNF TPN for preparations with 3.6g, 6.6g, 11.2g and 13.2g of nitrogen respectively. T-test showed a significant difference in favor of RTU TPN for all evaluated formulations (p <0.0001 for all). CONCLUSIONS The use of RTU offers a significant less costly alternative for adult TPN when compared with equivalent third-part CNF in Public Health Institutions in Mexico. The long-term adoption of the RTU TPN system can be associated with important cost-savings for public health institutions in Mexico.