It is well known that several medical drugs can increase MetHb concentration in the blood as a side-effect [26,27]. A recent review reports the early recognition, pathophysiology, and management of methemoglobinemia in the intensive care unit [28]. Chloroquine is such a drug for which reports were published regarding induced methemoglobinemia due to its intake [29,30,31]. Both chloroquine and hydroxychloroquine (a derivative of chloroquine) are currently used to treat COVID-19, while debate is ongoing about their effectiveness and safety [32,33,34,35,36,37,38,39]. Moderately certain evidence suggests that hydroxychloroquine lacks efficacy in reducing short-term mortality in patients hospitalized with COVID-19 or at risk of hospitalization in outpatients with COVID-19.