Dehydration: Alcohol is a diuretic. This means it encourages the body to lose more water than it takes on by halting the production of the body's anti-diuretic hormone. This means you feel the need to pee excessively, thus speeding up the loss of fluid from the body that leads to dehydration.
Alcohol also attacks our stores of vitamins and minerals, which need to be in the correct balance for the body to function normally. Dehydration caused by drinking can affect the balance by draining potassium from the body, resulting in thirst, muscle cramps, dizziness and faintness