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Why does alcohol affect people differently?

The effect of drinking the same amount of alcohol will vary from person to person. It depends on:

How fast you drink

If you drink quickly you will get a stronger effect than if you drink the same amount over a longer period. Drinking fast means the alcohol will build up in your blood stream faster than your liver can remove it.

If you have eaten 

If you eat before or during the time when you drink alcohol, it will have less effect on you. Food in your stomach slows down how fast the alcohol is absorbed into your blood.

Your weight

Alcohol will have a stronger effect on someone who weighs less. Larger people have more body fluids, which dilute the alcohol.

Your sex

Women are affected more than men. Women tend to have more a higher percentage of body fat and less fluid in their bodies than men. This means that alcohol is less diluted in women's bodies. Also, women don’t break down alcohol as efficiently as men, so the alcohol can build up in their blood stream.

Your age

Younger and older people are usually affected more. The amount of body fluids tends to decrease with age, so an older person will be more affected by the same amount of alcohol. Young people’s bodies are still developing and they usually have a lower tolerance for alcohol.

Your drinking history

People who don’t drink very often will be more affected than regular drinkers. People who are used to drinking develop a tolerance to the effects of alcohol as their body becomes used to it. Tolerance means that after regular drinking, you may find that drinking the same amount of alcohol no longer produces the same effect. Read more about tolerance

Your body type

An overweight person will be more affected than a lean, muscular person. Overweight people have more body fat and less fluids, so the alcohol they drink will be more concentrated in their blood.

Fizz

Fizzy drinks like champagne or drinks mixed with tonic or cola will affect you more quickly. The carbonation that produces the fizz increases the absorption of alcohol into the bloodstream.

Genetic factors

Some people have genetic differences that mean that they have different amounts of the enzymes that break down alcohol. This means they may get drunk more quickly. This variation is usually seen in certain populations of Asian descent, such as some Chinese and Japanese people.¹

What else changes how alcohol affects me?

Your mood and feelings

Your reaction to alcohol can change depending on your mood. It can make your mood more intense. For example, if you are feeling low, alcohol can make you feel more down after the initial buzz from drinking has worn off. We have more information on alcohol, feelings and your mood

Medication or drugs

If alcohol is mixed with other drugs, like illegal drugs or medicines, the combined effects can be unpredictable or dangerous. Read more about alcohol and medications.

¹ http://pubs.niaaa.nih.gov/publications/arh23-1/40-54.pdf

References 
www.drugs.ie/alcohol_info/about_alcohol/interactions_with_other_drugs/

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