The danger of low platelets is not dangerous is determined by the degree of low platelets, platelets <100*10^9 is considered thrombocytopenia, with the aggravation of platelet lowering, the risk of bleeding increases, when the platelets ≤20×10^9/L, the risk of spontaneous bleeding of vital organs and fatal cerebral hemorrhage is increased. The physiologic functions of platelets are clotting, hemostasis, and repair of broken blood vessels. Causes of low platelets include blood disorders, rheumatologic and immunologic disorders, antiplatelet drugs, and anti-inflammatory and analgesic drugs. If there is no comorbidity with other diseases and only low platelets are considered, generally speaking, platelets >50×10^9/L will not have bleeding symptoms or only show prolonged bleeding time from wounds; platelets ≤20×10^9/L can present the risk of spontaneous intracranial bleeding. If low platelets are present, with or without bleeding symptoms, it is important to visit a hematologist promptly for a thorough evaluation and to find the cause of the thrombocytopenia.