COVID-19, a highly contagious and rapidly spreading viral infection caused by the new corona virus SARS-COV-2, was first identified in China. On March11th, 2020 World Health Organization announced it a pandemic. The novel infection which is still being studied has a wide range of severity, ranging from no symptoms to severe pneumonia that can lead to death Objective: To find correlation between D-Dimer and platelets count with the severity of the disease Methods: It was a cross sectional study. The duration of the study was 6 months from November, 2020 to May 2021. The study was conducted in University Institute of Medical Laboratory Technology (UIMLT), University of Lahore. Data of 101 COVID-19 positive patients was taken from Shaukat Khanum Hospital, Farooq Hospital & University of Lahore Teaching Hospital (UOL), Lahore. Hematological and biochemical parameters such as Complete blood count (CBC), D-Dimer, Lactate Dehydrogenase (LDH), Platelet count (PLT) and Ferritin levels were observed. The data was analyzed using Statistical Package for Social Sciences (SPSS) Version 21.0. P-value less than and equal to 0.05 was taken as significant Results: Platelet count was decreased in severe patients of COVID-19 and was statisticallysignificant (P-value = 0.004) LDH, D-dimer, and Ferritin were increased with severity of disease and they were also statistically significant (P-value 0.005, 0.000. 0.027) respectively Conclusions:The platelet count, D-Dimer, LDH and Ferritin levels could act as the biomarker to determine the severity in COVID-19 infection