The guide

How your body clears alcohol

By GyroscopeUpdated November 14, 20269 sources

Your liver clears a fixed amount of alcohol an hour once the first drink or two is in, so one US drink takes most adults about 2 to 3.5 hours to mostly leave the blood, and every extra drink waits its turn. A meal lowers the peak and speeds clearing a little. Nothing else speeds it up.

People try a lot of things to get it out faster. Coffee, a cold shower, a glass of water, a walk around the block, a big greasy breakfast the next morning. Some of them make you feel more awake, which is why they seem to work. None of them lowers the alcohol in your blood. The liver does nearly all the work, and it has one speed.

Why can’t the liver go faster?

Think of your liver as a store with one checkout lane. When the first customer walks in, they go right through. Once the lane is busy, more customers don’t make it go faster. They wait in line, and the line moves at the same pace no matter how long it gets.

The cashier is an enzyme called alcohol dehydrogenase. It turns alcohol into acetaldehyde, a toxic chemical, mostly in the liver. A second enzyme, ALDH2, turns the acetaldehyde into acetate, which the rest of the body burns for energy. In a 1999 study with tracers, about 77% of the alcohol that left the blood was turned straight into acetate that went back into the blood.

The first enzyme gets saturated after the first drink or two. A 2010 review of the published rates found that above about 20 mg per 100 mL, your level falls by about the same amount every hour, whatever you drank. It’s 10 to 15 mg per 100 mL an hour on an empty stomach and 15 to 20 after eating, and 15 is a good average for moderate drinkers. The full range runs from 10 to 35, and the top of it is mostly people in alcohol detox, whose livers have built up a second clearing enzyme.

Once the level gets very low, the enzyme isn’t saturated anymore and the last bit clears more slowly. That tail is why the time to fully clear a drink is longer than simple division would give you.

How long does one drink take?

One US drink is 14 g of alcohol. How high that pushes your level depends on how much water is in your body, because alcohol spreads through body water. How long it lasts depends on that height and the liver’s fixed pace.

On our engine, with drinks spread over the first hour, food not known and an average liver, here’s the time from the first sip until it’s mostly cleared. The range in brackets is the same drinks for a liver at the fast and slow ends of the normal range.

Even the biggest body here, with the fastest liver in the normal range, takes about an hour and a half for one drink. The blood curve calculator draws your own evening, with the one-drink-an-hour line beside it so you can see the gap.

Why does the same drink hit women harder?

Alcohol lives mostly in body water, and pound for pound, women have less water in their bodies than men, according to NIAAA. After a woman and a man of the same weight drink the same amount, her level goes higher. It also lasts longer, since the liver still clears the same fixed amount an hour.

Body water isn’t fixed by sex alone. The number forensic scientists use for it, called the Widmark factor, changes with build too. In the published tables collected in a 2015 review, it runs from about 0.80 in a very lean man to 0.66 in a heavier man, and from about 0.74 in a lean woman to 0.53 or 0.60 in a heavier woman, depending on the method. The same review says any calculated level should come with a range, which is why every clear time on this site has one.

Women’s livers do clear a little faster for their size. The 2010 review found the fall in level is slightly steeper in women, likely because their livers are larger relative to their lean mass. It isn’t enough to make up for the higher starting level.

What does food do?

In a 1994 study, ten healthy men drank the same dose of alcohol twice, 0.8 g per kg of body weight, which is about four US drinks for a 165 lb man. Once was in the morning after an overnight fast. The other time was right after a breakfast of orange juice, fruit yogurt, two cheese sandwiches, a boiled egg and coffee with milk and sugar.

After breakfast, their peak was about a third lower, they felt less drunk, and the alcohol took about two hours less to clear. The meal slowed the alcohol on the way in, and it also sped up the liver. When the men ate a meal five hours after drinking, long after the alcohol had all gone in, their clearing rate still rose by 36 to 50%.

On our engine, three US drinks at 7, 8 and 9pm keep a 160 lb woman’s level up until about 4:30am on an empty stomach and about 2:20am with dinner. A big meal still doesn’t make a big evening short. A big meal soaks up the alcohol has the details.

Can anything else speed it up?

No. NIAAA says cold showers, hot coffee and walking don’t reverse the effects of alcohol. Caffeine can make you feel more awake. In a 2001 lab study of 15 adults, caffeine sped up one reaction test after drinking but not balance or a second reaction test, and people stayed slower than sober. Feeling sharper doesn’t mean the alcohol is gone.

The level can also keep rising after your last drink, because alcohol still in your stomach and gut keeps entering the blood. That’s why the curve on our calculators often peaks after the last glass, and why nobody should use a curve, a clock or a feeling to decide whether they can drive. Don’t drive after drinking.

How do our calculators work it out?

Every time on this site comes from one engine, built on the studies above.

• The pour. Grams come from ounces and strength, never from a drink’s name.
• The body. Each drink raises the level by its grams divided by body water, using Widmark’s averages of 0.55 for women and 0.68 for men, inside the published range.
• Going in. Each drink enters the blood over 30 minutes on an empty stomach, an hour if you’re not sure, and two hours with a meal. These windows are our own simplification. Against the breakfast study they understate what food does, which errs on the side of a later clear time.
• Coming out. The level falls by 15 mg per 100 mL an hour if you’re not sure about food, 12.5 on an empty stomach and 17.5 with a meal, slowing near zero the way the enzyme does.
• Mostly cleared. The clear time is when the level drops under 5 mg per 100 mL, where the enzyme has slowed right down.

It’s an average. It doesn’t know about medicines, liver disease, a GLP-1 drug, or how big your pour really was. Real people clear anywhere from 10 to 35 mg per 100 mL an hour, so your own time can be shorter or a lot longer than the middle number.