How Long Does Alcohol Stay In Your System?

Many people wonder how long they need to wait after drinking before it’s safe to say that they are 100% sober. You might have heard things like “one drink per hour” and other rules of thumb, but do you know the scientific facts behind alcohol’s presence in your system?

Here we’ll discuss how alcohol affects your body, along with the science behind how your body metabolizes alcohol, and the duration it remains in your system, so you no longer rely on "feeling sober" and instead know for a fact when alcohol is out of your system.

How Alcohol Affects Your Body

Before you decide that you “feel sober” and try to drive a car or do anything else, let’s talk about the different ways alcohol affects your body.

First, alcohol is a depressant that is rapidly digested by your body. In fact, if you were to drink on an empty stomach, 20% of the alcohol will immediately flow into your small blood vessels. The other 80% of the alcohol will go into the small intestine. Eating food can slow this absorption rate down, which is why people advise against drinking on an empty stomach.

Alcohol dramatically affects a person’s central nervous system. It poisons the brain, slowing it down. This can impair your motor functions and mental processing. Long-term abuse of alcohol can also lead to health issues like strokes, heart disease, liver disease, and different types of cancer.

How Alcohol is Metabolized

When alcohol enters your system, it is converted to a variety of substances before ultimately turning into water and carbon dioxide. Alcohol is essentially a poison, and your body makes it a priority to detoxify it. This means that your body will use its processes to deal with the alcohol first before any other nutrients.

Around 2-8% of the alcohol is expelled through sweat, urine, or your breath. The body metabolizes the rest. First, your body converts the ethyl alcohol into acetaldehyde and then further breaks it down into acetic acid. To help you make sense of these chemicals, acetaldehyde is essentially a poison for your body and is not too dissimilar to formaldehyde.

The other component, acetic acid, is typically an ingredient in vinegar that is eventually broken down into carbon dioxide and water.

To learn more about the science behind how alcohol is metabolized, we'd highly recommend you read this study from Arthur I Cederbaum, Ph.D.

Now that we've covered the science behind how your body handles alcohol let's get into the time periods that alcohol is detectable in your system.

How Long Does Alcohol Stay in Your Blood?

Blood Alcohol Content, also known as BAC, is one of the primary ways to determine how much alcohol is in your system at any given time. Typically, your body will eliminate alcohol at a rate of 0.015 units per hours. For example, if you were to have a BAC of .08, which is the legal limit for operating a vehicle in the U.S., it would take your body five and a half hours to flush the alcohol out of your body completely. Many people think that alcohol is flushed out much faster than this, so it’s important to know ahead of time.

How Long Does Alcohol Stay in Your Urine?

This answer is a little more complicated and significantly depends on the test that is used. Some tests can only detect alcohol for a few hours while others can detect EtG and EtS, which are metabolites of a drink you had several days ago.

The amount that a test can detect alcohol also depends on the amount you initially drink. When 5% of the alcohol reaches your kidneys, they'll immediately start expelling alcohol through urine. Alcohol can suppress a hormone that helps your body conserve fluid, which means your body secretes more fluids than usual.

How Long Does Alcohol Stay on Your Breath?

During traffic stops, law enforcement will typically test if a driver is over the legal limit through a breathalyzer. This measure the amount of alcohol on your breath and the more inebriated the person is, the higher the results will be. Typically, alcohol can stay on your breath for up to 24 hours after the last drink, but this also depends on the amount a person drinks in the first place.

Factors That Affect the Rate Alcohol is Processed

Much like many things in life, not everyone’s body functions the same. This is also true for the rate that your body processes alcohol. A few of the factors that affect the rate your body processes alcohol include:

Age

Do you feel like your body could handle alcohol easier when you were younger? You’re not alone. Your age can affect the rate that your body metabolizes alcohol. People between the ages of 20 and 30 can metabolize it faster than older individuals.

Sex

You’ve probably heard that women are more affected by alcohol than men, but have thought that was just a myth. In fact, there is science to back this claim up. One study finding that women experience more cognitive impairment under the influence of alcohol. Two factors lead to higher blood levels of alcohol in women than in men. One is that women tend to have lower amounts of an enzyme that breaks down alcohol in their stomachs. This enzyme is called alcohol dehydrogenase. As a result, more alcohol gets into the blood stream of women than men. The second factor is that women generally have less body water than men. This means alcohol is less diluted in women. Taken together, these two factors result in women having roughly twice the blood alcohol levels as men for the same amount of alcohol.

Body Weight

Have you heard the term “lightweight” used before to describe a person more susceptible to alcohol’s physical effects? This term is based on science, in fact. Heavier people tend to have lower BAC levels compared to lighter people that drank the same amount because they have more body water. The person’s build also affects this, as muscle tissue holds more water than fat tissue.

Time of Your Last Drink

As you have probably learned, alcohol can stay in your system for longer than you might think. The time of your last drink is one of the most significant factors in determining how long alcohol will stay in your system. If you keep drinking, alcohol will remain in your system even longer.

Carbonation

Although many people think that carbonation doesn’t play a role in how drunk a person gets or the rate alcohol is processed, it does. Non-carbonated drinks such as wine or liquor are absorbed by the body much slower than carbonated drinks like beer or champagne.

Alcohol Preparations

Finally, the proof and distillation of a spirit will affect how long it stays in your system. Spirits like vodka contain a higher water content than dark liquors, which means they’ll stay in your system for a shorter duration.

Summary

After reading all this, your previous estimate of the time it takes for alcohol to leave the system was probably on the shorter side. Alcohol can stay in your system for a while and leaves your body in different ways. There isn't one rule of thumb for determining the rate your body processes alcohol, but with all of these factors combined, you should have a better estimation.