Labile iron by iron formulation. Labile-free iron is elemental iron that has been released from the core of the iron/carbohydrate nanoparticle and available to bind transferrin. All formulations have the potential to cause infusion reactions from labile-free iron. The higher the labile iron content, the greater the likelihood of CARPA. FG and IS, with much smaller cores, releasing larger amounts of labile-free iron, require lower doses and more frequent visits to achieve the therapeutic dose. Reprinted from Jahn et al.¹⁴  with permission.