Platelet 3 usually refers to a platelet count of 3*10^9/L, which is dangerous. Platelets in human blood mainly play the role of hemostasis, when platelet count is severely reduced, its hemostatic ability is significantly weakened, the less severe condition can lead to bleeding site is difficult to stop bleeding, the serious condition can lead to spontaneous intracranial hemorrhage, internal organs bleeding and other serious bleeding manifestations, which can be life-threatening. The normal range of platelet count is 100~300*10^9/L. When the platelet count is less than 20*10^9/L, the risk of serious bleeding complications such as spontaneous intracranial hemorrhage and internal organ hemorrhage is extremely high and it is difficult to stop bleeding. Therefore, a platelet count of 3*10^9/L is very dangerous and requires immediate intravenous transfusion of single platelets of the same blood group to raise the platelet count. It is recommended that the patient should go to the hematology department immediately, complete the relevant examinations to identify the cause of thrombocytopenia, and then treat the cause of thrombocytopenia to improve the platelet count as soon as possible. The patient should avoid bumps and collisions on the way to the hospital to minimize the risk of bleeding on the way to the hospital.