According to the case reports of Kuipers et al. [17], Al-Aamri et al. [23], Palmer et al. [22], Faisal et al. [20], and Naymagon et al. [18], MetHb values for COVID-19 patients were above the reference range of 0.67 ± 0.33% for healthy non-smokers (Borland et al. 1985) with the highest MetHb value of >30% for a patient reported by Naymagon et al. [18].