Early detection and management of fluid overload are critically important in acute illness, as the impact of therapeutic intervention can result in decreased or increased mortality rates. Accurate fluid status assessment entails appropriate therapy. Unfortunately, as the gold standard method of radioisotopic fluid measurement is costly, time-consuming, and lacks sensitivity in the acute care clinical setting, other less-accurate methods are typically used, such as clinical examination or 24 h output. Bioelectrical impedance vectorial analysis (BIVA) is an alternative impedance-based approach, where the raw parameter resistance and reactance of a subject are plotted to produce a vector, the position of which can be evaluated relative to tolerance intervals in an R-Xc graph. The fluid status is then interpreted as normal or abnormal, based on the distance from the mean vector derived from a healthy reference population. The objective of the present study is to demonstrate how to evaluate the presence of fluid overload through bioelectrical impedance vectorial analysis and the impedance ratio measured with tetrapolar multi-frequency equipment in patients admitted to the emergency department.