Background: COVID-19 can infect an asymptomatic person silently without any overt symptoms despite diffuse blood clots throughout the body. Clot formation is induced by COVID-19 associated coagulopathy that can cause a high mortality rate. D-dimer, a fairly decisive marker for the coagulopathy event, is physiologically a marker of the fibrinolysis process. The increase of D-dimers in COVID-19 cases must be followed up because it relates to the initiation of a cytokine storm. Case presentation: We report an asymptomatic patient with sudden D-dimer elevation who received anticoagulant therapy. After three days of heparin administration, D-dimer results became normal and anticoagulant therapy was stopped. However, on the 12th day, the D-dimer level rebounded back and was followed by an increase of hs-C-reactive protein, erythrocyte sedimentation rate, IL-6, although SARS-CoV-2 PCR result became negative. A hyperglycaemic reaction and a sudden increase of HbA1C was observed in the patient. After three weeks D-dimer had returned to normal levels, and so did the other markers. The patient recovered fully and still no symptoms were obvious. Conclusion: COVID-19 patients without symptoms may be at risk of an asymptomatic coagulopathy process. The decreasing level of D-dimer erroneously cannot ensure that the coagulopathy process stops.