If you drink alcohol and suddenly faint without consciousness, there are usually several reasons as follows: 1, there is usually a hypoglycemic reaction, when people drink too much alcohol, there will be an increase in glycogen decomposition, a decrease in glycogen intake, a transient hypoglycemic reaction, blood glucose is lower than 3.9mmol/L, there will be a dizziness, a sudden fall of clinical symptoms, such as can not replenish the blood glucose in a timely manner, supplementing glucose, will be a further decrease in blood glucose, which will result in a hypoglycemic coma. Hypoglycemic coma, there will be sudden fainting and unconscious clinical symptoms. 2, common example of acute cerebrovascular disease in the drinking of alcohol cerebral blood vessels suddenly dilated, so that the cerebral hemodynamics of the brain accelerated significantly, at this time will be sudden cerebral hemorrhage, acute cerebral infarction or cerebral thrombosis of the sudden situation, can also lead to sudden fainting and unconsciousness. 3, such as drinking too much alcohol and led to a sudden alcohol intoxication, will also be sudden fainting and the surrounding unconsciousness. Sudden fainting and unconsciousness may also occur.