Isolated DC-DC converters are being considered for the power supply of water electrolyzers in the megawatt range to increase the overall plant efficiency and power density. Both the DC-DC converter and the water electrolyzer impose requirements on the Medium-Frequency Transformer (MFT), which is one of the core components. This article analyzes the efficiency challenge for MFTs as part of a DC-DC converter system to compete with a state-of-the-art water electrolyzer power supply. In order to reach the high efficiency requirements, the design parameters need to be varied, some of which are examined in more detail within this work. Thus, before the identification of decisive design parameters for a holistic design methodology, design considerations for MFT windings and core as well as insulation and cooling are analyzed.