Most people will metabolize alcohol, or get it out of their system, at a rate of about 0.016% per hour. This is known as your “burnoff” rate, and there is no effective way to speed it up.
Burnoff rate refers to how quickly your body can break down alcohol and remove it from your blood, also known as metabolizing it. As you metabolize the alcohol in your blood stream, you become less intoxicated. However, the burnoff rate is very slow and it can take hours to burn off a single drink. This means people often stay drunk far longer than they think.
Understanding alcohol burnoff rate is essential to many DUI cases, because DUI often depends on your blood alcohol concentration (BAC) at the time you were pulled over. Generally, if you had a BAC of .08% of more, it was illegal to drive. If it was less, you may have been legal after all. There are two main factors that affect your BAC, besides how much you drank:
- Your alcohol absorption rate, or how fast your body puts the alcohol you drink into your bloodstream
- Your alcohol burnoff rate, or how fast it removes it
Basically, BAC is a juggling act between these two factors. Whenever you drink, your stomach and small intestine start working to absorb the alcohol into the blood, and your liver starts working to get rid of it. Unfortunately, your body can generally absorb alcohol much faster than it can break it down and burn it off, which is why you can feel drunk long after you stop drinking.
How does the body break down alcohol?
When you start drinking, the liver uses an enzyme called alcohol dehydrogenase. This enzyme essentially attaches to a molecule of ethanol (alcohol) and breaks it down. In most cases, unless you are binge drinking or extremely drunk, this is your body’s only way to remove alcohol from the system. (In those extreme cases it can produce a second enzyme, called CYP2E1, but this is rare. If you are drinking that heavily, you are not safe to drive and you may need hospitalization.)
Alcohol dehydrogenase is only produced by the liver and the liver can only produce so much at once. This means that your body has a fixed, limited rate at which it can burn off alcohol.
How fast do I burn off the alcohol I drink?
Your burnoff rate is measured by how fast your body can decrease your BAC percentage. The rate for everyone is about .016% per hour. So, for example:
- If your BAC is .10 (over the legal limit)…
- …and you wait one hour…
- …it will have gone down by .016%, to a total of .084%—still over the limit.
In fact, if your alcohol started at .10%, it would take you over six hours of no drinking to become completely sober.
Is the burnoff rate different from person to person?
No. In most ways, everybody’s body is unique, and we all know that some people metabolize things differently than others. But this isn’t the case for alcohol breakdown. This is because alcohol dehydrogenase can only work so fast, one alcohol molecule at a time. It doesn’t matter whether you are a man or woman, 6 feet tall or 5 feet tall, or whether you had a light beer or a hard liquor. Your body can only break down alcohol at a rate of about .016% per hour, and any difference from person to person is tiny.
There are two exceptions to this:
- If you ate before drinking, you may break down alcohol slightly faster. This is probably because a full stomach increases blood flow and liver activity. However, the difference is not a big one—it will still take a long time to break down alcohol. And eating after you start drinking doesn’t help at all.
- If you are a heavy drinker or alcoholic, you can potentially develop cirrhosis of the liver. This condition inhibits liver function and you will take even longer to burn off alcohol.
Is there any way I can speed up my burnoff rate?
No. There are many tricks that people try, such as drinking coffee, taking a shower, drinking water, or “sleeping it off.” These tricks can help in other ways, helping you feel more alert (coffee) or prevent dehydration and hangover (water), but they don’t change how drunk you are, and they don’t speed anything up. Even if you feel alert because of lots of caffeine, if your BAC is over a certain limit you have the same poor reflexes and decision making as any other intoxicated person.
So how long do I have to wait to be safe to drive?
There is no single strict rule. Unfortunately, although the rate at which you break down alcohol is very consistent, the rate at which you absorb it can vary widely. You can even continue to absorb alcohol into your blood stream long after you stop drinking, meaning you keep getting drunker with no more drinks. This is called rising BAC.
There are some estimates that people often give. For example, if you drink only one drink per hour, you can expect to burn off one drink as you start the next one, maintaining a mostly level BAC for the entire time you’re drinking. But this is a rule of thumb at best, and it won’t work as well for some people as it does for others.
If you use a BAC calculator, however, you can find out almost exactly what your BAC is—as long as you’re honest about the size and strength of the drinks you consumed. And if you know your BAC, you can subtract .016% per hour to know how many hours it will take to be completely sober.
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