Health Encyclopedia

Understanding Alcohol's Effects

What happens when you drink alcohol? Everybody reacts in a different way to it. But in general, it is quickly absorbed into your blood. The amount of alcohol in your blood peaks within 30 to 45 minutes after your last drink.

Alcohol is also metabolized by your body. That means it is broken down chemically so it can be removed. Alcohol is broken down more slowly than it is absorbed. As a result, you can become drunker if you take in more alcohol than is removed. Your blood alcohol level will then go up.

Many factors influence how you react to alcohol. These are:

  • Your genetics

  • Body weight

  • Sex

  • Age

  • Type of beverage you drink

  • Amount of food in your stomach

  • Medicine in your system

  • Your overall health


Three enzymes break down alcohol. People can have variations of the gene that makes these enzymes. As a result, their bodies may break down alcohol in a different way. For instance, different levels of these enzymes cause facial flushing, nausea, and a rapid heartbeat in many people with East Asian heritage. These people may not like to drink. Genetics may also help explain why some ethnic groups have higher or lower rates of problems linked to alcohol.

Your weight

The extent of alcohol's effect depends on how much is in your blood and how much blood you have. That’s because alcohol is spread throughout your body by the water in your bloodstream. The more water in your blood, the more diluted the alcohol will be.

Generally, the lower your body weight, the less blood and water you have. That’s why smaller people often have more alcohol in their blood if they drink as much as a heavier person.

Your sex

Men can normally drink more alcohol than women before they show its effects. It’s true even if a man and woman are the same size. That’s because women have less body water than men who weigh the same. Women tend to have a higher concentration of alcohol in their bodies after drinking the same amount.

Women also have lower levels of one of the enzymes that breaks down alcohol. So the alcohol they drink stays in their bodies for a longer time. A woman's brain and other organs are exposed to more alcohol and its toxic byproducts.

Your age

As people grow older, they often have a higher fat-to-muscle ratio. They also have less body water. If they drink as much as younger people of the same weight, they may have a higher amount of alcohol in their blood. Many older people also take medicine that may interact with alcohol. Plus, they often have slower reaction times and problems with seeing and hearing. That puts them at higher risk for falls and traffic accidents.

The type of beverage

A standard drink is 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of 80-proof distilled spirits. All these have the same amount (about 15 grams or 1/2 ounce) of alcohol. But keep in mind that the alcohol content of many types of beer, wine, and distilled spirits can vary a lot.

People tend to feel the effects of beer or wine a little less. That may be because the water in beer and wine creates more volume to drink compared with hard liquor. The carbon dioxide in champagne or soda in a mixed drink raises the rate of alcohol absorption. It causes a more rapid effect.

How much food is in your stomach

The rate at which alcohol is absorbed depends on how quickly the stomach empties its contents into the intestines. Foods high in fat take longer to leave the stomach. If you eat a meal before you drink, the alcohol will be absorbed much slower than if you drink on an empty stomach. Your blood alcohol level will be lower.

The medications you take

Alcohol can affect how some medicines work. For instance, any drug that can cause drowsiness, such as a sleeping pill, can make you feel drunker. Be sure to ask your health care provider if any of your medicines can have this effect.

Your physical and emotional health

People who are fatigued or highly stressed often have a stronger reaction to alcohol. That’s true even if they drink a moderate amount.

Medical Reviewers:

  • Holloway, Beth, RN, M.Ed.
  • MMI board-certified, academically affiliated clinician
  • Turley, Ray, BSN, MSN