Transferrin in the blood is saturated with iron normally by:

Transpo of Fe2+ into the enterocytes occurs divalent metal transpoer 1 (DMT1). Some is stored in ferritin. A protein called hephaestin (Hp) is associated with ferropoin 1. It is not a transpoer itself, but it facilitates basolateral transpo. In the plasma, Fe2+ is conveed to Fe3+ and bound to the iron transpo protein transferrin. This protein has two iron-binding sites. Normally, transferrin is about 35% saturated with iron, and the normal plasma iron level is about 130 microg/dL (23 mumol/L) in men and 110 micro g/dL (19 mumol/L) in women. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 26. Digestion, Absorption, & Nutritional Principles. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.