F2 and COVID-19: Platelet, d-dimer and fibrinogen were significantly associated with severity. No correlation was evident between an increased severity risk and activated partial thromboplastin time or prothrombin time. Coagulation dysfunction is closely related to the severity of patients with COVID-19, in which low platelet, high d-dimer, and fibrinogen upon admission may serve as risk indicators for increased aggression of the disease.