Sudden blackness and dizziness may be a normal phenomenon, or it may be caused by myocardial infarction, cerebral hemorrhage and other diseases. 1. Normal phenomenon: long time squatting, blood stagnation in the lower limbs, when getting up too fast, may lead to insufficient blood supply to the brain, thus appearing in front of the eyes of the sudden blackness, dizziness symptoms. This is generally a normal phenomenon, and can be relieved after rest. 2. Myocardial infarction: Myocardial infarction may cause a decrease in the contraction function of the heart, leading to a decrease in the heart’s ability to eject blood, resulting in insufficient blood supply to the brain, which leads to the symptoms of sudden blackness and dizziness. 3. Cerebral hemorrhage: Cerebral hemorrhage may result in increased intracranial pressure, which affects the blood circulation of the brain and may lead to ischemia and hypoxia of the brain tissues, resulting in the symptoms of sudden blackness and dizziness. In addition, anemia, Meniere’s disease and other symptoms of sudden blackness and dizziness may also occur, and it is recommended that patients go to the hospital in a timely manner after ruling out the normal phenomenon, so as not to delay the condition.