Aim: The study aimed to observe and compare the demographic, comorbidities, biomarkers in different categories of diagnosed COVID-19 patients admitted to a COVID dedicated tertiary care hospital in the pic time of the pandemic, 2020, at Dhaka, Bangladesh. Methods: This retrospective study was conducted from May to September 2020 in 720 bed Holy Family Red Crescent Medical College Hospital. Four hundred seventy-three patients included in this study, diagnosed by RT-PCR of the nasopharyngeal swab, were divided into four groups. The mild group includes 254 patients, the moderate group has 82 patients, 38 patents in the severe group, and the critical group who were admitted to ICU, 99 patients. Demographic data, available investigation reports of individual patients, obtained from hospital records manually and compared between all four different categories of patients.