The possible effects of ionizing radiation on four commercial membranes, which are typically used as electrolytes in fuel cells supplying energy to a huge variety of medical implantable devices, were studied. These devices could obtain energy from the biological environment through a glucose fuel cell, which could be a good candidate to replace conventional batteries as a power source. In these applications, materials with high radiation stability for the fuel cell elements would be disabled. The polymeric membrane is one of the key elements in fuel cells. Membrane swelling properties are very important because they affect the fuel cell’s performance. For this reason, the swelling behaviors of various samples of each membrane irradiated with different doses were analyzed. Each sample was irradiated with a typical dose of a conventional radiotherapy treatment, and the regular conditions of the biological working environment were simulated. The target was to examine the possible effect of the received radiation on the membranes. The results show that the ionizing radiation influenced their swelling properties, as well as that dimensional changes were dependent on the existence of reinforcement, be it internal or external, in the membrane structure.