Your body clears alcohol at a fairly steady rate of about one standard drink per hour. That means if you have four drinks, you’re looking at roughly four to five hours before your blood alcohol level drops back to zero. But “in your system” can mean different things depending on what’s being tested, and some detection methods can pick up traces of alcohol days or even months after your last drink.
What Counts as One Drink
Before you can estimate how long alcohol will stay in your system, you need to know what a “standard drink” actually contains. In the United States, one standard drink has 0.6 ounces (14 grams) of pure alcohol. That equals 12 ounces of regular beer at 5% alcohol, 5 ounces of wine at 12%, 8 ounces of malt liquor at 7%, or a 1.5-ounce shot of 80-proof liquor. A lot of people undercount their intake because a single cocktail or a large pour of wine can easily contain two or three standard drinks.
How Your Body Processes Alcohol
Your liver does nearly all the work. It breaks down alcohol at a remarkably constant pace, lowering your blood alcohol concentration (BAC) by about .015 to .020 per hour. That translates to roughly one standard drink per hour, and nothing speeds it up. Coffee, cold showers, and food won’t help your liver work faster once alcohol is already in your bloodstream. Time is the only thing that clears it.
What food can do is slow absorption before alcohol hits your blood. Drinking on a full stomach means alcohol enters your bloodstream more gradually, so your peak BAC will be lower and you’ll feel the effects less sharply. But the total time your body needs to eliminate the alcohol doesn’t change much, because your liver still processes it at the same fixed rate regardless of how quickly it arrived.
After your last drink, your BAC continues rising for a short period as alcohol finishes absorbing from your stomach and small intestine. If someone at .08 BAC (the legal driving limit in most states) stops drinking, it takes roughly four to five hours to get back to zero.
Detection Windows by Test Type
How long alcohol shows up on a test depends entirely on what’s being tested. Here’s how the common methods compare:
- Breath test (breathalyzer): Detects alcohol for about 12 to 24 hours after your last drink. This is what law enforcement typically uses during traffic stops.
- Blood test: Similar to breath, blood tests pick up alcohol for roughly 12 to 24 hours. Both breath and blood are snapshots of recent drinking.
- Standard urine test: Alcohol itself can be detected in urine for about 12 to 24 hours.
- EtG urine test: This test looks for a metabolite your body produces when it breaks down alcohol, not the alcohol itself. It can theoretically detect drinking up to 80 hours after your last drink, but experts generally consider it reliable only within the first 24 hours. After that, the chance of a false negative climbs significantly. Courts often use a higher detection threshold (500 nanograms per milliliter versus the standard 100), which shortens the practical detection window even further.
- Hair follicle test: The longest window by far. Alcohol markers can appear in a hair strand test for one to six months, though it takes several weeks after drinking for the markers to show up. This test captures a pattern of use over time rather than a single drinking session.
Factors That Affect How Long It Takes
While the average rate is one drink per hour, several things push that number up or down. Body weight matters because a larger body has more water to dilute alcohol, resulting in a lower BAC from the same number of drinks. Biological sex plays a role too: women generally have a higher proportion of body fat and less of the enzyme that begins breaking down alcohol in the stomach, so they tend to reach higher BAC levels from the same amount.
Age gradually slows alcohol processing because liver function declines over time. People with liver damage or liver disease will clear alcohol more slowly, sometimes significantly so. Interestingly, research published in Gastroenterology found that people who drink heavily on a regular basis actually develop a faster clearance rate while actively drinking, because their liver ramps up a secondary alcohol-processing pathway. That elevated rate drops back to normal within about three weeks of stopping.
Medications that are processed by the liver can also compete with alcohol for the same metabolic pathways, potentially slowing clearance of both the drug and the alcohol.
Why You Still Feel Bad After Alcohol Clears
Your BAC can be back at zero and you can still feel terrible. Part of that is dehydration and disrupted sleep, but congeners also play a role. Congeners are chemical byproducts created during fermentation and aging, and they’re found in higher concentrations in darker drinks like whiskey, red wine, brandy, and tequila. Methanol, one of the most studied congeners, can linger in the body after all ethanol has been eliminated, which may explain why hangover symptoms persist well past the point when you’d pass a breathalyzer. Clear liquors like vodka and gin contain fewer congeners and tend to cause less severe hangovers.
Alcohol and Breast Milk
For nursing parents, the timeline is specific. Alcohol levels in breast milk peak 30 to 60 minutes after a drink. As a general rule, alcohol from one drink can be detected in breast milk for about two to three hours. Two drinks extend that to four to five hours, and three drinks to six to eight hours. The alcohol leaves breast milk as it leaves your bloodstream, so pumping and dumping doesn’t speed up the process.
A Quick Reference by Number of Drinks
These are rough estimates for a person of average weight and health, based on the standard metabolism rate of one drink per hour:
- 1 drink: About 1 to 2 hours to clear from blood
- 2 drinks: About 2 to 3 hours
- 3 drinks: About 3 to 4 hours
- 4 drinks: About 4 to 5 hours
- 5 drinks: About 5 to 6 hours
These numbers assume you’ve stopped drinking. If you’re drinking over several hours, the clock doesn’t start until your last drink is absorbed, and your liver has been working through earlier drinks the whole time. So someone who has five beers over four hours won’t need a full five additional hours, because the liver was already processing throughout the evening. Still, the safest approach is to give yourself more time than you think you need, not less.