Fe-59 is an isotope of iron. It has a half-life of 44.5 days and decays by emitting a beta particle. In medicine, ferrous citrate Fe 59 is indicated, by intravenous administration, to determine various parameters of the kinetics of iron metabolism, including plasma iron clearance, plasma iron turnover rate, and the utilization of iron in new red blood cells. An oxidized form of iron cation, ferric cation Fe59, is also used to study the processes of iron metabolism.