The recent developments of medical applications of electromagnetic fields in both diagnostic and therapeutic scenarios has posed the attention on the accurate knowledge of the dielectric properties of human tissues. Accordingly, several studies were recently devoted to the measurements of such properties under various physiological conditions. Since biological tissues show a high variability, to compare the different data it is necessary to thoroughly control the experimental conditions. In this work, an ex vivo study is performed on rat fat tissue to look for possible confounders linked to the time between excision and measurement. © 2018 FESB, University of Split.