Platelets only 4, refers to the platelet count of 4 × 10^9 / L, how long can live is not yet accurate data. However, platelet 4×10^9/L is a very dangerous situation, patients need to go to the hospital immediately for treatment to avoid affecting the safety of life. Platelet 4×10^9/L is a very serious condition, which can cause spontaneous internal bleeding, intracranial hemorrhage and so on, leading to the patient’s death. It can be seen in primary immune thrombocytopenia, acute leukemia, aplastic anemia and so on. Patients should go to the hospital immediately for platelet transfusion to keep platelets above 20×10^9/L to reduce the risk of bleeding. Patients with bleeding tendency should apply hemostatic drugs (tranexamic acid, etc.) to promote the body to stop bleeding. At the same time, etiological treatment is carried out, such as acute myeloid leukemia is given chemotherapy with drugs such as cytarabine and Zoerythromycin. There is no clear data on how long patients with platelets 4×10^9/L can live. For patients with thrombocytopenia, relevant examinations should be improved in time to clarify the cause of the disease. Patients with thrombocytopenia caused by primary disease need to actively control the primary disease. Specific diagnosis and treatment should be carried out under the guidance of physicians.