Background: The D-dimer is formed by the activation of the plasmin enzyme, and elevated levels indicate that there is a hypercoagulable state and secondary fibrinolysis in the body, which is extremely useful for the diagnosis of thrombotic diseases. Patients with COVID-19 were reported to have a hypercoagulable state. Patients and methods: This study included 231 out 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. Results: 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, This study reveals high plasma D-dimer levels in 84 patients (36.4%), which was a significant biomarker for COVID-19 diagnosis in out-hospitalized patients (Outpatients and patients under home observation), with a p-value is 0.00001 which less than 0.05. Conclusion and Recommendations: False data about D-dimer was caused more deaths in Egypt for patients and physicians, they thought Anticoagulation therapy was only for hospitalized patients and not for out-hospitalized patients with moderate infection, they thought the D-dimer test is not important for out- hospitalized patients, but this study showed a high level of D-dimer 36.4% in out- hospitalized patients with COVID-19, so 36.4% of outpatients and patients under home observation need Anticoagulation therapy to decrease the complications of COVID-19 infection, Many individuals with diabetes and immunosuppressive diseases it is known that they face a higher probability to experience serious complications from COVID-19 infection so Anticoagulation therapy is suggested before the elevation of D-dimer level to avoid serious complications.