You’re off work for the weekend, so you meet some friends for drinks on Sunday. You’re having a good time, but it’s getting late in the day, and you have an early shift in the morning. Your friends ask you to stay for one more round, and you’re not sure. As a commercial driver, you know how important safety is, not just for you but for everyone else on the road.
Alcohol can stay in your system and affect your driving for hours after your last drink. Understanding how long alcohol stays in your body is crucial–it’s not just a matter of failing DOT breath alcohol testing; it can be the difference between life and death on the road.
The speed with which your body eliminates alcohol is dependent on your age, body mass, sex, genetics, overall health, and how much you drink. Before we get into how to determine how long after a drink you should wait to drive, we will go over how your body metabolizes alcohol.
How Your Body Processes Alcohol
When you take a drink, your body starts processing alcohol almost immediately. Some of the alcohol is absorbed in your stomach, but most is absorbed through your small intestines, where it immediately makes its way into your bloodstream. It travels through your body via the central nervous system. You can feel the effects of alcohol within minutes.
Alcohol is a central nervous system depressant, meaning that it affects and impairs signals being sent to your brain. In small doses, it makes you feel more relaxed and less anxious, but in larger doses, it can lead to a dramatic lowering of inhibitions, feelings of euphoria, or anger and aggression. Other effects of alcohol that can seriously impact your ability to drive include slower reaction times, impaired decision-making, loss of coordination and balance, distorted depth perception, drowsiness, and reduced focus.
Your body eliminates alcohol much more slowly than it absorbs it. One standard drink will increase your blood alcohol by about 0.02%, but your body can only remove about 0.016% per hour. That means even if you only have one drink an hour, your blood alcohol concentration will continue to increase. The only thing that will lower the concentration of alcohol in your system is time. The more you drink, the longer it will take to metabolize and leave your system.
Factors that Impact Detection Time
We can give some estimates of how long alcohol will stay in your system, but it is based on averages, and everyone’s body processes alcohol differently. Here are a few factors influencing how long you can detect alcohol through a breath or blood test.
Sex
Women generally have proportionally more body fat and less body water than men, which means that alcohol tends to stay in their system longer.
Ethnicity
Studies have found that individuals of East Asian descent don’t produce as much of a key enzyme that breaks down alcohol in the liver. As a result, they have trouble metabolizing alcohol, and it will linger in their bodies for longer.
Age
As you get older, your liver becomes less efficient at metabolizing alcohol, so it takes longer to excrete alcohol and eliminate it from your system.
Food Consumption
Because 20% of alcohol is absorbed in the stomach, and 80% is in the small intestines, the longer alcohol stays in your stomach, the longer it takes to absorb and the longer it takes to be eliminated. Therefore, if you drink on a full stomach or snack while drinking, it will take longer for you to feel the effects of alcohol, and it will reduce the intoxicating impact, but it will also take longer for the alcohol to leave your body.
Medications
Many medications are known to interact with alcohol and may impact how your body absorbs alcohol and how long it stays in your system. You must talk to your doctor about the relationship between your prescription medications and alcohol. Some medicines that are known to interact with alcohol are anti-anxiety meds, ADHD medications like Adderall, cough and cold medications, and diabetes drugs.
Blood Alcohol Levels
A person’s blood alcohol concentration (BAC) is the percentage of alcohol in a person’s bloodstream. A person is considered legally intoxicated and is prohibited from driving a car when their BAC is at 0.08% in the U.S. However, most people can start to feel the impact of alcohol at much lower levels–around 0.05%.
The rules for commercial drivers are much more strict. The legal limit for commercial drivers is 0.04%. Drivers are subject to random drug and alcohol testing, and they are required to submit to testing after significant traffic accidents or if they are suspected of being intoxicated. Failing to take a test or having a blood alcohol level over 0.04% can result in a one-year disqualification from driving and fines or criminal penalties if the violation results in an accident.
How to Eliminate Alcohol from Your System
Unfortunately, the only way to get rid of alcohol from your bloodstream is to wait. Nothing else can make it go faster–not drinking coffee or water, exercising, sleeping, showering, or even vomiting.
You need to understand your own body, but on average, here are some guidelines for how long alcohol will show up on different kinds of tests:
Blood Test: Alcohol is eliminated from your bloodstream at a rate of around 0.016% per hour. Depending on how much you drank, it can take up to 12-24 hours before a blood test will come back negative.
Breath Test: A breath test has the same timeline as a blood alcohol test. If you’ve had a lot to drink, you’ll need to wait 12-24 hours before DOT breath alcohol testing will come back negative.
Urine Test: Alcohol can be detected with an EtG urine analyzer three to five days after you drink. It will take 10-12 hours after drinking for a traditional urine test to come back negative.
FMCSA Regulations
Federal Motor Carrier Safety Association (FMCSA) regulations stipulate that commercial drivers are not allowed to consume alcohol or be under the influence of alcohol within four hours of going on duty or operating a commercial motor vehicle.
However, as explained before, depending on your body and how much you drank, you may need to wait much longer than four hours to operate a motor vehicle legally and safely.
Staying Aware and Staying Safe
It is possible to drink moderately if you are a commercial driver, but you have to be extra aware of your limits, how much alcohol you are consuming, and how long before you drive again. Knowing how long alcohol stays in your system will help you be sure that you are compliant with DOT regulations and that you are safe. Even small amounts of alcohol can impair your judgment, slow your reaction times, and put you and others at risk. If you are in doubt, err on the side of caution. Prioritizing responsible drinking habits can save your job and maybe even your life.
