Your size
If you are small, your blood volume is much less than that of someone who is larger. You are, therefore, likely to be affected more by the same amount of alcohol than someone much larger than you.

Your water level
If you are dehydrated, alcohol will have a much greater effect than if your body's water concentration is normal. This is why drinking alcohol in the summer or after exercise will affect you more.

Your gender
Women are generally smaller than men and they also have proportionately less body water. Therefore, they are more easily affected by alcohol.

The amount of food in your stomach
If you drink one unit of alcohol on an empty stomach, almost all the alcohol will be absorbed within an hour. However, if there is food in your stomach this process will be slowed down, and the alcohol will reach your brain and other parts of your body more slowly.

How often you drink
People who drink regularly become less affected by alcohol as their bodies get used to it. They then need to drink more for it to have the same effect. This is called developing a tolerance to alcohol.