Based on this information, and the importance of transferrin isoforms in delivering oxygen to the tissues through its involvement in iron metabolism [12], the aim of this study was to evaluate the association of the serum profile of transferrin isoforms with the severity of COVID-19 disease (i.e., COVID-19 severity scale of World Health Organization, presence of cytokine storm, oxygen therapy and chronic disease, the value of modifited early worning score—MEWS) and to compare this profile to the profiles in other diseases. Here, TF is linked to COVID-19.