Short-term effects of alcohol consumption include intoxication and dehydration.

Long-term effects of alcohol include changes in the metabolism of the liver and brain and alcoholism.

Alcohol intoxication affects the brain, causing slurred speech, clumsiness, and delayed reflexes. Alcohol stimulates insulin production, which speeds up glucose metabolism and can result in low blood sugar, causing irritability and (for diabetics) possible death. Severe alcohol poisoning can be fatal.

4,5 ‰ is the concentration of blood alcohol that is fatal in 50% of the test subjects. That is about six times the level of ordinary intoxication, but vomiting or unconsciousness may occur much sooner in people who have a low tolerance for alcohol. The high tolerance of chronic heavy drinkers may allow some of them to remain conscious at levels above 4‰ although serious health dangers are incurred at this level.

Alcohol also limits the production of vasopressin (ADH) from the hypothalamus . This is what causes severe dehydration when large amounts of alcohol are drunk. It also causes a high concentration of water in the urine and vomit and the intense thirst that goes along with a hangover.

A study found that lifelong abstainers were 2.36 times more likely to suffer a stroke than those who regularly drank a moderate amount of alcohol beverages. Heavy drinkers were 2.88 times more likely to suffer a stroke than moderate drinkers.