Your body eliminates alcohol at a fixed rate of about 0.015 BAC per hour, which means a single drink typically clears your bloodstream in one to two hours. But “out of your system” depends on what you mean: alcohol can show up on a breath test for up to 24 hours, in urine for up to five days, and in hair for months. Here’s what determines how long it actually takes.
How Your Body Breaks Down Alcohol
Almost all alcohol processing happens in the liver, using two enzymes that work in sequence. The first converts alcohol into a toxic compound called acetaldehyde (a known carcinogen). The second quickly breaks acetaldehyde down into acetate, which your body then converts to water and carbon dioxide for easy removal.
This process runs at a relatively steady pace. Your liver clears roughly 0.015 grams per 100 milliliters of blood every hour. In practical terms, that’s about one standard drink per hour for most people. You can’t speed it up with coffee, cold showers, or exercise. Once alcohol is in your bloodstream, your liver sets the clock.
What Counts as One Drink
A standard drink in the United States contains about 14 grams of pure alcohol. That’s a 12-ounce beer at 5% alcohol, a 5-ounce glass of wine at 12%, or a 1.5-ounce shot of spirits at 40%. Many real-world servings exceed these amounts. A craft IPA at 8% alcohol, a generous wine pour, or a strong cocktail can easily equal 1.5 to 2 standard drinks, which doubles the time your body needs to process it.
A Rough Timeline for Clearance
If you have three standard drinks over the course of an evening, your BAC might peak around 0.06 to 0.08 depending on your size and other factors. At the elimination rate of 0.015 per hour, reaching 0.00 from a peak of 0.06 takes about four hours. From 0.08, closer to five and a half hours. A heavier night of drinking with a peak BAC around 0.15 could take ten hours to fully clear.
This is why someone who drinks heavily on a Saturday night can still have measurable alcohol in their blood on Sunday morning. The math is straightforward: divide your estimated peak BAC by 0.015 to get the approximate number of hours until your blood is alcohol-free.
Detection Windows by Test Type
Different tests detect alcohol (or its byproducts) for very different lengths of time:
- Blood: Up to 12 hours after your last drink.
- Breath: Up to 24 hours. Breathalyzers measure alcohol still being exhaled from the lungs, so they track closely with blood levels but can pick up traces slightly longer.
- Saliva: Up to 24 hours, similar to breath testing.
- Urine (standard test): 12 to 24 hours for a basic alcohol screen.
- Urine (EtG test): Up to 3 to 5 days. This test looks for a metabolic byproduct rather than alcohol itself. In a study of heavy drinkers, EtG remained detectable for a median of about 78 hours, with some individuals testing positive beyond 100 hours.
- Hair: 1 to 6 months. Hair follicle tests capture a long-term record of alcohol use, though it takes several weeks after drinking for markers to appear in a hair sample.
For workplace testing under Department of Transportation rules, a breath alcohol concentration of 0.02 or higher is recorded as a positive result, and 0.04 or higher counts as a violation. These are well below the 0.08 legal driving limit, so even residual alcohol from the night before can cause a failed test.
Why It Takes Longer for Some People
The 0.015-per-hour figure is an average. Several biological factors shift your actual rate up or down.
Body composition matters more than body weight alone. Research from the University of Illinois found that lean body mass, meaning total weight minus fat, is the strongest predictor of how fast women eliminate alcohol. The connection is likely because more lean mass correlates with more functional liver tissue. In that study, women with obesity eliminated alcohol at an average rate of 9 grams per hour, compared to 6 grams per hour for women at a healthy weight, because they carried more lean mass overall despite having higher body fat percentages.
Biological sex also plays a role. Women generally have a higher proportion of body fat and less total body water than men of the same weight, which means alcohol becomes more concentrated in their blood after the same number of drinks. The result is a higher peak BAC and a longer total clearance time, even when the liver works at the same rate.
Age can slow things down. Liver function gradually declines with age, and the same study found age influenced elimination rates, particularly in older women.
How Food Changes the Equation
Eating before or while drinking doesn’t help your liver work faster, but it does change how quickly alcohol reaches your bloodstream. Food in your stomach slows absorption, which lowers your peak BAC. A lower peak means less total time until you reach zero.
The type of food matters somewhat. In a study of 51 male volunteers, a high-carbohydrate meal significantly reduced peak blood alcohol levels compared to drinking on an empty stomach. A high-protein meal, interestingly, did not have a significant effect on peak levels. Either way, food reduces the height of the spike rather than the speed of elimination.
What You Can and Can’t Control
You can’t make your liver metabolize alcohol faster. No supplement, food, or activity changes the 0.015-per-hour rate in any meaningful way once alcohol is in your blood. What you can control is your peak BAC: drinking fewer drinks, spacing them out over more hours, eating beforehand, and choosing lower-alcohol beverages all result in a lower peak and a shorter total clearance window.
If you’re concerned about a specific test, the detection window depends entirely on the type. Standard blood and breath tests only catch recent drinking within roughly 12 to 24 hours. EtG urine tests can flag alcohol use from several days prior. And hair tests create a months-long record that a single night of heavy drinking can leave a mark on.