This paper defines the minimal dosimetric requirements for in vivo studies that are (1) average and peak spatial specific absorption rate (SAR) values for the whole body and specific organs, (2) the uncertainty of each assessed SAR value, and (3) the short term and long term SAR variations between the tissues of individual animals. Without this information, the results of non-thermal end-points cannot be discussed nor can different studies be compared. A methodology to obtain this pertinent dosimetric information is developed and proposed in this paper. To demonstrate the methodology, it was applied to the PERFORM A setup for exposing rats at 1747MHz.