Magnesium and its alloys have a great potential to be used as degradable biomaterials for clinical applications, which only need temporary support. However, the corrosion of Mg under physiological conditions is not well understood yet. The aim of this study was to determine the effect of proteins and complex corrosion environments. The corrosion rates of dysprosium containing magnesium alloys in technical and physiological corrosion set-ups were compared. Moreover, pure magnesium was immersed under cell culture conditions in simple and complex protein solutions. Corrosion rates showed huge variations depending on the corrosion environment. Proteins delayed corrosion and altered the ion composition of the solutions. In conclusion, the choice of appropriate corrosion environment is crucial for in vitro experiments.