Background: Lactate dehydrogenase (LDH) is an intracellular enzyme found in cells in almost all organ systems, which catalyzes the interconversion of pyruvate and lactate, LDH has been proved to be a prognostic factor with
high accuracy in diseases involving multiple organ injuries such as acute heart failure (AHF) and severe acute pancreatitis (AP), LDH is a potential prognostic biomarker in patients with COVID-19. Patients and methods: This study included 217 non hospitalized patients with confirmed COVID-19 infection in Alexandria, Egypt, these study subjects were randomly selected irrespective of the age group and both genders were included, Assay procedure as manufactory instructions and Reagents of Chema Diagnostics Italy, LDH FL of reagent based on  DGKC recommendations. Results: The percentage of COVID-19 non hospitalized Patients relation to the serum LDH level, The present study included patients aged from14 years to 75 years mean age was 44.5 ±30.5 who were confirmed to have Covid-19 based on real-time reverse transcription-polymerase chain reaction, female gender was more frequent (n=119, 54.8%) than Male gender (n=98, 45.2%). This study reveals high serum LDH levels in 147 patients (67.7%), which was a significant biomarker for COVID-19 diagnosis in non-hospitalized patients (Outpatients and patients under home observation), with a p-value is 0.024 which less than 0.05. Conclusion and Recommendations: Serum LDH level is a good biomarker of infection in COVID-19 Outpatients and patients under home observation increased by 67.7%, many other studies revealed LDH is a good marker for COVD-19 hospitalized patients and severe infection.