The danger of increased blood viscosity is mainly caused by hyperlipidemia, hypertension, cerebral thrombosis and other diseases. 1. Hyperlipidemia: due to the increase of blood viscosity, it is easy to make a lot of lipids attached or deposited on the wall of blood vessel, resulting in the elevation of blood lipid level and hyperlipidemia, and long-term hyperlipidemia is easy to cause atherosclerosis, which results in the blockage of blood vessel, leading to the insufficiency of blood supply to the whole body, and making patients suffer from infarction, dizziness, palpitation and other uncomfortable symptoms. 2. Hypertension: due to the increase of blood viscosity, it will lead to the increase of resistance in the blood, which will make the peripheral resistance of the blood vessels increase, resulting in hypertension, aggravating the burden on the heart, which will make the patients suffer from dizziness, convulsions, shortness of breath and other uncomfortable symptoms. 3. Cerebral thrombosis: When the blood viscosity increases to a certain degree, it will easily lead to the aggregation of platelets in the blood and eventually induce cerebral thrombosis. Patients will have blurred vision, numbness and weakness of limbs, and in severe cases, quadriplegia and coma will result. Patients with increased blood viscosity are advised to go to a specialized hospital to clarify the cause of the disease and under the guidance of a doctor for further examination and treatment.