Whether you’re spending time with friends or trying to unwind after a long day, many of us enjoy having a cocktail or cracking open a cold beer occasionally.

While consuming alcohol in moderation is unlikely to be harmful, drinking in excess can have considerable negative health effects.

But how exactly does alcohol affect your body? How much alcohol is too much? And are there ways to drink safely? Continue reading as we explore the answers to these questions and more below.

When we drink alcohol, its first destination is the stomach. It’s here that alcohol begins to be absorbed into your bloodstream.

If you don’t have food in your stomach, the alcohol will likely pass into your small intestine rather quickly. The small intestine has a much higher surface area for absorption than your stomach, meaning alcohol will enter your blood faster.

If you’ve eaten, your stomach will be focused on digesting the food. Therefore, alcohol will move out of your stomach more slowly.

Once in the bloodstream, alcohol can move to other organs of the body, including the liver. The liver is responsible for breaking down most of the alcohol that you consume.

How the body metabolizes alcohol

Inside the liver, alcohol is metabolized, or broken down, in a two-step process:

  • Step 1: An enzyme called alcohol dehydrogenase breaks down alcohol to a chemical called acetaldehyde.
  • Step 2: A different liver enzyme called acetaldehyde dehydrogenase breaks down alcohol into acetic acid.

The cells of your body break acetic acid down further into carbon dioxide and water. These compounds can be easily eliminated from your body via processes like urination and breathing.

So what exactly gives us that tipsy, drunk feeling? Your liver can only metabolize so much alcohol at a time, which means that alcohol can travel through the bloodstream to other organs, such as the brain.

Alcohol is a depressant of your central nervous system (CNS). That means it has a slowing effect on your brain.

Because of this, the neurons in your brain fire off nerve impulses more slowly. This can lead to things like the impaired judgment or coordination that’s associated with drunkenness.

Alcohol can also stimulate the release of neurotransmitters like serotonin and dopamine. These neurotransmitters are associated with pleasure and reward and can lead to feelings like happiness or relaxation.

These feelings are joined by additional physical symptoms of intoxication such as flushing, sweating, and increases in urination.

A hangover occurs after you drink too much alcohol. Symptoms can be unpleasant and can vary by person. Here’s what causes a hangover:

  • Dehydration. Alcohol consumption causes an increase in urination, leading to fluid loss. This can lead to headache, fatigue, and feeling thirsty.
  • Irritation of the GI tract. Alcohol irritates the lining of the stomach, leading to nausea and stomach pain.
  • Sleep disruption. Drinking often leads to poor sleep, which can increase feelings of tiredness or fatigue.
  • Low blood sugar. Alcohol can lead to low blood sugar, which may cause you to feel tired, weak, or shaky.
  • Acetaldehyde. Acetaldehyde (the chemical formed from alcohol metabolizing in your body) is toxic and can contribute to inflammation in your body, which can make you feel like you’re sick.
  • Mini-withdrawal. Alcohol has an inhibitory effect on your CNS. When the alcohol wears off, your CNS is out of balance. This can lead to feeling more irritable or anxious.

Blood alcohol concentration (BAC) is the percentage of alcohol in a person’s bloodstream. As you consume additional alcohol, more and more of it enters your bloodstream.

Many factors affect how alcohol is absorbed and metabolized. These include:

  • Sex. Due to differences in alcohol metabolism, women typically have a higher BAC than men after the same amount of drinks.
  • Weight. After the same number of drinks, people with a higher body mass are more likely to have a lower BAC than someone with a lower body mass.
  • Age. Younger people may be less sensitive to some of the effects of alcohol.
  • Overall health and whether you have any underlying health conditions. Some conditions can affect the body’s ability to metabolize alcohol.
  • Levels of alcohol metabolism and tolerance. The rate of alcohol metabolism and the level of alcohol tolerance can vary between individuals.

Several outside factors can also affect your blood alcohol levels. These include:

  • the type and strength of the alcohol you’re drinking
  • the rate at which you’ve consumed alcohol
  • the amount of alcohol you’ve had
  • whether or not you’ve eaten
  • if you’re using alcohol with other drugs or medications

Legal and illegal limits of BAC

The United States has defined a “legal limit” for BAC. If you’re found to be above the legal limit, you’re subject to legal penalties such as arrest or a DUI conviction.

In the United States, the legal BAC limit is 0.08 percent. The legal limit for drivers of commercial vehicles is even lower – 0.04 percent.

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Is there a way that you can tell your level of intoxication? The only way that BAC levels can be measured is by using a breathalyzer test or a blood alcohol test.

The charts below may be helpful for reference. They show the weight, legal limits, and levels of intoxication for men and for women.

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Blood alcohol percentage levels for men.
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Blood alcohol percentage levels for women.

According to the Dietary Guidelines for Americans: 2020–2025, a standard drink is defined as 14 grams (or 0.6 ounces) of pure alcohol.

Remember that alcohol levels can vary by specific beverage. For example, by these guidelines, 12 ounces of an 8 percent beer is technically more than one drink. Similarly, a mixed drink such as a margarita likely contains more than one drink as well.

So what are some good guidelines for moderate levels of drinking? The Dietary Guidelines for Americans: 2020-2025 defines moderate drinking as up to 1 drink per day for women and 2 drinks per day for men.

Moderate drinking is defined as up to 1 drink per day for women and 2 drinks per day for men.

These guidelines are generally safe for most people. Some other recommendations for safe alcohol consumption include:

  • Be sure not to drink on an empty stomach. Having food in your stomach while drinking can slow alcohol absorption.
  • Make sure to stay hydrated. Try to drink a full glass of water between each drink.
  • Sip slowly. Try to limit your consumption to one drink per hour.
  • Know your limits. Decide how many drinks you’re planning on having before starting. Don’t let others pressure you to drink more.

While drinking in moderation is unlikely to be harmful for most people, binge drinking or chronic drinking can become dangerous. When does drinking become worrisome?

Problematic drinking includes the following:

  • Binge drinking, which is defined as 4 drinks in 2 hours for women and 5 drinks in 2 hours for men.
  • Heavy drinking, which is having 8 drinks or more per week for women and 15 drinks or more per week for men.
  • Alcohol use disorder, which involves symptoms like being unable to curb your drinking, requiring more alcohol to achieve the desired effect, and continuing to drink despite its negative effects on your life.

Health risks of alcohol

There are many potential health risks associated with misuse of alcohol. Some of them include:

People who should avoid alcohol

There are some groups that should avoid drinking altogether. They include:

  • people who are under the legal drinking age, which is 21 in the United States
  • pregnant women
  • people who are recovering from alcohol use disorder
  • people who are planning to drive, operate machinery, or participate in another activity that requires coordination and being alert
  • people taking medications that can have a negative interaction with alcohol
  • people with an underlying health condition that could be negatively affected by alcohol

You should see a doctor if you think you or a loved one might be misusing alcohol. Look out for these signs:

  • You feel like you drink too much or can’t control your drinking.
  • You find that you spend a lot of time thinking about alcohol or trying to acquire alcohol.
  • You’ve noticed that drinking has had a negative impact on your life, including your work, your personal life, or your social life.
  • Family, friends, or loved ones have expressed their concern about your drinking.

If you identify with any of these signs, talk to a doctor. They can work closely with you to develop a strategy to help you stop drinking.

If you notice these signs in a friend or loved one, don’t be afraid to reach out and express your concerns. Staging an intervention may help them to realize they need to get help for their drinking.

Consuming alcohol in moderation is unlikely to have a negative effect on your health. However, misusing alcohol can have a variety of harmful effects.

If you do choose to drink, it’s important to do so safely. This can be accomplished through slowing your intake, staying hydrated, and not drinking more than you can handle.

If you believe that yourself or a loved one is misusing alcohol, be sure to speak to a doctor. There are also other ways to get help, including the SAMHSA National Helpline (800-662-4357) and the NIAAA Alcohol Treatment Navigator.