Plasma membrane ferroxidase that mediates the extracellular conversion of ferrous/Fe(2+) iron into its ferric/Fe(3+) form. Couples ferroportin which specifically exports ferrous/Fe(2+) iron from cells to transferrin that only binds and shuttles extracellular ferric/Fe(3+) iron throughout the body (PubMed:22961397, PubMed:37277838). By helping iron transfer from cells to blood mainly contributes to dietary iron absorption by the intestinal epithelium and more generally regulates iron levels in the body (By similarity). {ECO:0000250|UniProtKB:Q9Z0Z4, ECO:0000269|PubMed:22961397, ECO:0000269|PubMed:37277838}. This is the function of HEPH (hephaestin, Ensembl gene identifier ENSG00000089472).