A headache after drinking alcohol may be related to hangover, or it may be caused by insufficient blood supply to the brain, migraine, high blood pressure and other reasons. 1. Hangover: After resting overnight due to excessive drinking, the alcohol in the body, i.e. ethanol, has been completely eliminated, but there are still symptoms such as headache, dizziness, fatigue, nausea, etc. This is because the liver cells are unable to metabolize the harmful substances such as ethanol after drinking. This is because after drinking a large amount of alcohol, the liver cells are unable to remove all the harmful substances after alcohol metabolism, such as acetaldehyde and other symptoms of acute poisoning. 2. Insufficient blood supply to the brain: after drinking alcohol into the blood circulation of the human body, it will form a stimulus to the cerebral blood vessels, leading to cerebral blood vessel diastolic and contractile function disorder, resulting in insufficient blood supply to the brain, which will cause headaches. 3. Migraine: Especially for those who have a history of migraine, after drinking alcohol, it will stimulate the brain nerves and induce migraine attacks, which can cause headache symptoms, and in severe cases, nausea, vomiting, photophobia, phonophobia and other symptoms may also occur. 4. Hypertension: Especially people with a history of high blood pressure, after drinking alcohol, it will lead to an increase in sympathetic excitability, resulting in an increase in heart rate, myocardial contraction, which in turn induces an increase in blood pressure, which can cause headaches, and may also be accompanied by nausea, vomiting and other symptoms. Drinking headache should pay attention to rest, if the symptoms continue to be unable to relieve, should seek medical attention as soon as possible, after a clear diagnosis of symptomatic treatment.