The process of alcohol metabolism is a complex one, and there is no straightforward answer to how long alcohol stays in your system. As a guideline, you may have heard that a person processes about 1 unit of alcohol per hour. For a guesstimate, this is pretty accurate. However, there are many factors that can change that.
Of course, how much you drink will determine how long alcohol remains in the body, but one’s weight, gender, metabolism, tolerance and other factors will affect it as well.
What Is A Unit?
A unit of pure, 100% alcohol is about 10mL. However, no alcohol sold has a 100 ABV (alcohol by volume), so it has to be calculated. The units in a drink can be calculated if you know the amount used and the alcohol percentage. The exact formula is:
Units = Total Volume (mL) x ABV (%)
Example: One Wine Bottle (750mL) of 13% ABV
(750 x 13) = 9.75 units
A drink is not the same as a unit. A drink depends to a standard portion size. For example, a glass of wine can be measured in 125mL, 175mL, and 250mL portions. However, wine varies by strength, so a small glass can have 1.3 or 2 units. A large can have 2.5 or 3.5 units.
As a quick reference:
A standard 175mL glass of 12% wine is about 2 units
A 250mL glass of 12% wine is 3 units
A pint of 3.6% beer is two units
A pint of 5.25% beer is three units
A 25mL shot of any 40% spirit (vodka, whiskey, gin) is one unit
If you don’t want to do the math, you can use DrinkAware’s online calculator to check how many units (and calories) are in your beverage.
The Process of Alcohol Metabolism
After being consumed, alcohol first makes its way into your stomach, where about 20% is directly absorbed into your bloodstream. The rest, like food, makes its way through your digestive system, and is absorbed from the small intestine.
Once the alcohol hits the bloodstream, it will travel around the body first affecting the brain, then the rest of the organs. Once the alcohol has made its way around, only then it is metabolised by the liver, before it is excreted, mainly via urine, sweat, or saliva.
All parts of the body, with the exception of bone and fat tissue, absorb any alcohol that is consumed, making it possible to be detected long after a person has stopped drinking.
Although alcohol’s effects can be felt within 15-45 minutes after consumption, it can take up to an hour for it to be absorbed by the rest of the body. It is only after that time that the process of metabolism begins.
Factors That Affect How Long Alcohol Stays in Your System
The are a number of factors that determine how fast alcohol is absorbed and how long it remains in the body. The faster the alcohol is absorbed and the faster it is metabolised, the faster it leaves the body.
Type and Amount of Alcohol
Obviously, the more you drink, the more the body has to process. The type of beverage matters as well. Remember, alcohol metabolism depends on the number of units, not the number of drinks had. A bottle of wine will be metabolised faster than a bottle of vodka.
Alcoholic drinks mixed with water or fruit juice, or those consumed with food, will be absorbed more slowly into the bloodstream. However, fizzy drinks and certain mixers will be absorbed faster.
Because alcohol is a diuretic, it will affect the water levels in the body. If a person drinks a lot, they will become dehydrated, which will increase how long alcohol stays in the system.
A person’s weight and levels of fat and water will determine how well they absorb and metabolise alcohol. Having more fat and less water percentage will result in higher alcohol blood levels. Having a lower body mass means less muscle tissue to help metabolise it.
Women tend to have less body mass than men, as well as a higher fat percentage and lower water percentage. Women also have less alcohol dehydrogenase, an enzyme responsible for metabolising alcohol. This makes them more prone to alcohol’s effects as the alcohol remains in the blood longer.
Hormonal levels make a difference as well, which is why alcohol has stronger effects during menstruation and ovulation. Contraceptive pills, too, have an effect, slowing down the alcohol metabolism process.
As a comparison, if two drinks take men an hour to process, they can take women three hours.
Certain races, largely those from East Asia, carry specific genes that prevent the complete metabolism of alcohol into acetic acid, causing a buildup of acetaldehyde, a toxic compound responsible for the feeling of unpleasantness associated with drinking too much. This can affect alcohol metabolism as well, and have an impact on how long alcohol stays in your system.
When discussing age, body mass again plays a role. Younger people tend to have a lower weight than adults and less muscle tissue. This may also be the case for much older people. Older people also may have a less active overall metabolism, slower blood flow, and decreased liver function. They may also be taking medication, which can affect how long alcohol stays in the body.
People with a higher tolerance will metabolise alcohol faster. One’s tolerance levels take time to develop. If a person drinks for a long period and in large amounts, over time, the body will adjust itself to improve its alcohol metabolism. This applies to drugs as well.
A person’s general health, especially their liver function, will have an effect as well. Any medication that a person takes can alter how long alcohol remains in the body. Stress, anxiety, depression, or other mental distress can also make a difference. Stressful circumstances lower metabolic enzymes in the body, preventing proper alcohol processing.
How Long Can Alcohol Be Detected in your System?
Tests for alcohol can vary, and many focus not only on sobriety but also on whether alcohol is or has been present in the body over a period of time. There are many tests that can be used but the most common ones use breath, blood, hair, saliva or urine.
A breathalyser measures the amount of alcohol (ethanol) in the breath, and uses that information to estimate the blood concentration. They can detect alcohol in your breath for up to 24 hours after consumption. They are mainly used to check for levels of sobriety in the moment.
Alcohol stays in the blood until it is metabolised, thus it largely depends on the amount that was consumed. The higher the BAC (blood alcohol concentration), the longer the alcohol will stay in the body. If the BAC is about 0.08 (the driving limit), it can be detected for about 6 hours.
With urine, it largely depends on the sensitivity of the test. Unlike blood tests, urine tests check for alcohol metabolites, not the presence of alcohol itself. Most of them can detect alcohol between 12 and 24 hours after consumption. However, there are ultra-sensitive tests that can detect alcohol consumption 5-7 days after.
A cheek swab also tests for alcohol metabolites, and detects the presence of alcohol 10-24 hours after consumption.
Alcohol can also be detected in breast milk and sweat. With breast milk, alcohol is detectable as long as it is present in the blood. With sweat, the range is between 1-4 hours.
All hair on the body records a history of any drug use. With alcohol, and most other substances, the hair retains traces for about 3 months.
Can I Speed Up the Process of Removing Alcohol from the Body?
How long alcohol stays in the system depends on the amount consumed and one’s metabolism. Although aforementioned factors have some say, ultimately the process of alcohol metabolism is non-negotiable. Drinking water and coffee can help slow the absorption of alcohol and sober you up, but the alcohol still has to be metabolised eventually. Any promises of speedy alcohol removal from the body are myths.
How Soon Can I Drive After Drinking?
From a theoretical perspective, a person may drive after drinking if they are under the legal limit. However, any amount of alcohol in the system can be considered intoxication if you were to have an accident. Any amount of alcohol can also affect your ability to operate a vehicle safely.
Acceptable alcohol intoxication levels vary by country. In the Republic of Ireland, the limit is a BAC of 0.05.
For reference, if you drank two 125mL glasses of wine or 2 pints of beer, it would put you just over the 0.05 limit. It would also take about 2-3 hours for your body to process it, including consumption and absorption time.
Remember, it takes about one hour for your body to process a unit of alcohol. You can refer back to the unit calculator if you feel unsure. However, it is always best to avoid driving when you plan on drinking. Even if you feel sober, it is better to be safe.
If you find that you are frequently asking yourself if you are safe to drive, or if you have alcohol in your system, you may have a problem with substance abuse. Contact us at Smarmore Castle for more information, and help.