The purpose of this study was to evaluate potency changes in insulin in different solutions and bag materials used for peritoneal dialysis (PD). One of the PD solutions (Physioneal) tested is available in two different solution containers, PVC and Clear-Flex. Four insulin concentrations (4 IU/L, 10 IU/L, 20 IU/L, and 40 IU/L) were evaluated. This range of concentrations was defined in accordance with standard medical practice. All PD solutions made by Baxter, Castlebar, Ireland. Insulin determination was performed by immunoassay (ELISA). In Dianeal, more than 90% of the initial dose of insulin remained available up to 24 hours for all concentrations tested. In Physioneal, for the higher concentrations tested (10 IU/L, 20 IU/L, and 40 IU/L), more than 90% of the initial dose of insulin remained available up to 6 hours, and more than 80% up to 24 hours. For the Lowest concentration of insulin tested in Physioneal (4 IU/L), more than 90% of the initial dose of insulin remained available up to 3 hours, and more than 70% up to 24 hours. Also for the lowest concentration of insulin, recovery correlated with the pH of the tested solutions. This effect became apparent over the storage time. The data show that insulin adsorption is less than 10% during the first 3 hours for every PD solution tested. Insulin recovery tends to be stable or to decrease slightly over time for the lower insulin concentrations tested. The results for insulin recovery show a correlation with insulin concentration and with pH for the lowest insulin dose tested. From a solution-container interaction perspective, Clear-Flex is an equivalent alternative to standard PVC material.