Model for LMM Iron Trafficking in Healthy Blood: Nutrient iron is imported through FPN, oxidized by HFN, and transferred to apo-TFN in a channelled step in which no FeIII intermediate forms. During red-cell recycling, low-mass FeII species from liver and kidney macrophages are proposed to be released into the blood. They become oxidized by CPN to the FeIII state, coordinated to apo-TFN, and then trafficked to the bone marrow for erythropoiesis as well as to organs as needed. The proposed LMM FeII/III intermediates may be those detected in this study.