Did you know alcohol use can be detected months after your last drink?

By Maggie O'Neill
June 20, 2019

We’ve all been warned not to drink and drive. We’ve been taught that alcohol use and driving don’t mix well. But how long does alcohol stay in your system? Should you worry about driving, say, the morning after a night out with friends? We asked an expert to explain just how long it takes your body to rid itself of alcohol.

For starters, we’ll give you a refresher on what happens to your body when you drink. You’ve probably heard that alcohol use—depending on how much you drink—can harm your liver. But you may not have been warned about just how much stress you put on this vital blood-filtering organ after even just a few hours of partying.

“When you get alcohol in your blood, it passes through the liver, and the liver breaks it down,” explains George Koob, PhD, director of the National Institute on Alcohol Abuse and Alcoholism, a division of the NIH.

The main job of your liver is filtering blood that’s flowing from your digestive tract to the rest of your body. In the process of breaking down the alcohol you consume, your liver encounters toxins. Heavy drinking can make your liver fatty and cause scarring that can eventually restrict blood flow. This can cause liver cells to die and, consequently, halt liver function.

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So, how long does alcohol stay in your system? Individuals metabolize alcohol at different rates. In general, Koob says most people can break down half a drink every hour. He also explains it in terms of your blood alcohol content (BAC). “If you’re at 0.08, if you don’t drink anymore, in two hours you’d probably be [at] about 0.05,” he says. So, that translates to your BAC lowering at about 0.015 an hour. (In the US, your blood alcohol content is calculated as a percentage of the grams of alcohol you’ve consumed per every 100 milliliters of your blood.)

A Breathalyzer measures your BAC by calculating how much alcohol is in the air you blow onto it. For reference, you can get a DUI if you drive while having a BAC of 0.08 or higher. If you weigh 160 pounds, four drinks can put you there. Again, keep in mind that people’s bodies react differently to alcohol. All the averages you hear when it comes to alcohol use are just that. What happens to your friend when she has four drinks might not be exactly what happens to you if you try to drink as quickly as her.

Now that you know how long it takes a person (on average) to metabolize alcohol, you might wonder how long it takes for your body to completely rid itself of the drug. According to addiction treatment network American Addiction Centers, “Alcohol is detectable for up to 6 hours in blood; about 12-24 hours in breath, urine, and saliva; and up to 90 days in hair.”

So just because you’ve endured the hangover doesn’t mean someone can’t tell that you partied over the weekend if they get ahold of a hair sample.

For reference, a small glass of red wine has around 1.5 units of alcohol. (One unit of alcohol is eight grams or 10 milliliters of pure alcohol.) A pint of strong beer has around 3, and a small shot of tequila has about 1. You’ll be doing your body a favor if you keep count of how many units you’ve consumed while you’re hanging out at the bar. If you keep count, you’ll know when it’s time to slow down and stop.

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