After you drink alcohol enters your blood stream through the stomach walls and small intestine. The liver then starts to produce an enzyme called alcohol dehydrogenase (ADH) which starts to break down the alcohol. The rate at which the alcohol in your body is broken down depends on a number of factors such as your weight, gender, age, medication, how much you've eaten and obviously how many units you have drunk. Depending on the strength of the beer it can take your body 2-3 hours to completely break down the alcohol in a standard pint of beer, as a healthy adult can usually metabolise a unit of alcohol every hour, taking into account the factors mentioned before. Although it is generally considered that a pint of beer has 2 units in it, this has been shown to vary, while lager generally has a higher alcoholic content with a pint from a pub containing almost 3 units. If you consume a lot of alcohol there is a chance that there will be some left in your blood stream, sometimes enough for you to be over the legal limit which in the UK is 80mg of alcohol for every 100ml of blood. For this reason men can generally drink more than women and therefore women are recommended not to drink more than 2-3 units a day whereas men can drink 3-4 a day before it becomes a medical concern. It is important to consider this as driving or operating machinery can be a lot more dangerous after drinking, as alcohol impairs some brain functions and increases reaction times. Other effects of alcohol include dehydration.
