HBG2 and COVID-19: It cannot be ruled out that a transient increase in HbA1c levels during the acute period of COVID-19 may be associated with specific SARS-CoV-2 structure and replication and primary disruption of erythropoiesis According to the results of previous studies, erythrocytes are one of the target cells in COVID-19, which is further proved by potential abnormalities in such forms of hemoglobin, as carboxyhemoglobin, methemoglobin, [38] or hypoxia and SpO2 decrease in many patients.