Background and aim: The exact pathophysiology of a COVID-19 infection is still not completely understood, which complicates treatment of the disease. In order to clarify the pathophysiologic mechanisms and optimize treatment methods, monitoring of the sublingual microcirculation may be valuable. From studies in septic patients, we know that microcirculation is impaired and that the microcirculation better describes severity of illness than different macrocirculatory parameters. In this study, we aimed to investigate the changes of the microcirculation and the macrocirculation over time in patients with a COVID-19 infection who were admitted to the ICU and see if this was different in patients who are more or less severely ill based on SOFA score. Materials and methods: Macrocirculatory and microcirculatory measurements were performed as soon as possible after admission to the ICU (T0) and then at 24 and 48 hours (T1 and T2). Patients were divided into subgroups based on the median SOFA score to make a distinction between more and less severely ill patients. To investigate the development of the macrocirculatory and microcirculatory parameters over time and to compare this in patients with different severity of illness, a linear mixed model analysis was performed. Results: 21 COVID-19 patients were included for analysis. The median SOFA score was 8 and no differences were found in clinical and demographic patient characteristics between SOFA groups. Patients in the low SOFA score group had higher PaO2 values and lower lactate levels compared to patients in the high SOFA score group (p = 0.033 and p = 0.007 respectively). In the low SOFA score group, mean PPV and mean FCD were higher compared to the high SOFA score group (p = 0.018 and p = 0.034 respectively). TVD showed a trend towards significance, with higher mean TVD values for patients in the low SOFA score group. Discussion: We found that microcirculation parameters measured at T0 were not significantly different between patient subgroups. Analysis of the course of the microcirculation over 48 hours (T0-T2) however, shows that for less severely ill patients PPV and FCD remain higher than for more severely ill patients. So, there may be a relationship between severity of illness of patients with a COVID-19 infection and the ability to activate microcirculatory compensatory mechanisms in order to draw on reserve capacity in a situation of hypoxemia.