Abstract : Background: Coronavirus Disease 2019 (COVID-19) is a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) related illness that has spread globally and may worsen as pulmonary fibrosis develops. Krebs von den Lungen-6 (KL-6) has been recommended as a marker of COVID-19 and the severity of the illness. It is a chemical that is mostly expressed by injured alveolar type II cells. In order to confirm KL-6 potential as a predictive biomarker of severity in patients with COVID-19, this pilot investigation measured blood concentrations of KL-6. Materials and Methods: One hundred and forty patients with COVID-19 participated in the research. According to the severity of the disease, the COVID-19 patients were classified into three groups: critical disease (n=43), severe disease (n=52), and mild/moderate disease (n=45), with (n=60) healthy volunteers as the control group. Blood samples were taken as well as all of the patients' fundamental clinical and demographic information.