˝ In this cohort study of 1641 adult patients with SARS-CoV-2 infection who were hospitalized, elevated RDW at admission and increasing RDW during hospitalization were associated with statistically significant increases in mortality risk. The association between the RDW at admission and mortality risk was independent of D-dimer (dimerized plasmin fragment D) level, absolute lymphocyte count, demographic factors, and common comorbidities.˝
I think hemoglobin concentration increases as an adaptive response to decreasing PaO2 levels attributed to breathlessness caused by Covid 19 infections.
Abdounasser Albasher Omar A very good question indeed. We didn't found any specific changes except mildly elevated ESR and some sporadic changes in DC from which we couldn't come into an inference that it happened due to covid-19 infection.
Little is known. For "COVID-19 AND hemoglobin" search in Pubmed. There are few articles listed.
About oxygen affinity read:
Vogel DJ, Formenti F, Retter AJ, Vasques F, Camporota L. A left shift in the oxyhaemoglobin dissociation curve in patients with severe coronavirus disease 2019 (COVID-19). Br J Haematol. 2020;191(3):390-393.