Study aim: Comparing the effects of melatonin and placebo tablets on the: 1- recovery duration of clinical symptoms (fever, cough and myalgia) 2-improvement time of the laboratory parameters 3-duration of radiology- symptoms remission Design: The confirmed and suspicious COVID-19 patients who have been admitted to Bohlool Hospital and meet the study criteria are randomly assigned to the two groups of intervention and control. At the group allocation stage, the groups are homogenized in terms of age, gender and illness. Also, the number of confirmed and suspicious patients will be equal in the two groups. Then, for preventing medication interference all the prescriptions are assessed by two specialist doctors. Settings and conduct: The research will be conducted at Bohlool Hospital. At admission, all patients are given 200 mg of hydroxychloroquine every 12 hours as the main treatment of COVID-19. Then, the pharmacist will give the two weeks supply of melatonin and placebo tablets to the researcher in numbered packages, neither of them knows the content. In the medication group, 3 mg melatonin tablets are given three times a day for 2 weeks. In the placebo group, vitamin B containing tablets with the same appearance are given with the same method and duration as the main medicine. Participants/Inclusion and exclusion criteria: The consent to participate The confirmed and suspicious COVID-19 patients Not participating in other clinical trials simultaneously Intervention groups: Initially, all patients are treated according to the standard treatment of Ministry of Health (Hydroxychloroquine 200 tablets every 12 hours for 14-17 days). Then, the patients are divided into two groups: one group is given the melatonin tablet as an intervention group, the other group will receive a placebo tablet containing vitamin B. Main outcome variables: COVID-19