Sudden fainting and loss of consciousness after drinking may be related to alcohol poisoning, or may be caused by hypoglycemia, myocardial ischemia, acute cerebrovascular disease and other reasons. 1. Alcohol poisoning: If you drink too much alcohol at one time, it is easy to produce strong inhibition of the central nervous system, which may cause dizziness and drowsiness, and in serious cases, it may cause respiratory depression, resulting in a lack of oxygen in the brain, which may lead to sudden fainting and loss of consciousness. 2. Hypoglycemia: after drinking alcohol, especially after drinking a large amount of alcohol, alcohol in the body metabolic process is easy to induce insulin secretion, and will inhibit the secretion of hepatic glycogen, resulting in a decrease in blood glucose, when the blood glucose is too low, there may be a sudden fainting, loss of consciousness. 3. Myocardial ischemia: after drinking alcohol, along with the alcohol into the blood circulation, easily lead to vasodilatation, which may cause a drop in blood pressure, when the body is in a state of low blood pressure, it is easy to cause myocardial ischemia due to the obstacle of blood circulation, resulting in cardiac arrhythmia, or even cardiac arrest, which may be manifested in sudden fainting and loss of consciousness. 4. Acute cerebrovascular disease: If you suffer from high blood pressure and other basic diseases, drinking a lot of alcohol may induce acute cerebrovascular disease, such as acute cerebral hemorrhage, which will lead to sudden fainting and loss of consciousness. Sudden fainting and loss of consciousness after drinking may also be caused by other reasons, and you should go to the hospital in time to get a clear diagnosis of the cause and then be treated under the guidance of the doctor.