Alcohol is typically eliminated from your bloodstream at a fixed rate of about 0.015 BAC per hour, which means a single drink clears in roughly one to two hours. But “in your system” can mean different things depending on the test. A standard blood or breath test detects alcohol for only a matter of hours, while a urine test looking for alcohol metabolites can pick up evidence of drinking two or three days later.
How Your Body Processes Alcohol
After you take a drink, alcohol is absorbed quickly and can be measured in your blood within 30 to 70 minutes. If you’ve eaten recently, absorption slows, pushing that peak later. Once alcohol reaches your liver, an enzyme breaks it into a toxic intermediate compound called acetaldehyde, which is then converted into acetate and eventually into water and carbon dioxide that your body easily eliminates.
Your liver does nearly all of this work, and it operates at a mostly fixed speed: about one standard drink per hour. A standard drink in the United States contains 14 grams of pure ethanol, roughly the amount in a 12-ounce beer, a 5-ounce glass of wine, or a 1.5-ounce shot of liquor. Drinking faster than your liver can process simply causes alcohol to accumulate in your blood.
Detection Windows by Test Type
How long alcohol shows up depends entirely on what the test is measuring.
- Blood and breath tests detect alcohol itself. Because your body clears alcohol at about 0.015 BAC per hour, these tests generally return to zero within 12 to 24 hours after your last drink, depending on how much you consumed.
- Standard urine tests also detect alcohol directly, with a detection window similar to blood testing, roughly 12 to 24 hours.
- EtG urine tests look for ethyl glucuronide, a metabolite your body produces when processing alcohol. After a few drinks, EtG can show up in urine for up to 48 hours. With heavier drinking, that window extends to 72 hours and sometimes as long as 80 hours.
- Hair tests can detect alcohol metabolites for up to 90 days, though they are less commonly used and better at identifying patterns of heavy drinking than a single episode.
Doing the Math on Your BAC
Because elimination is roughly linear at 0.015 BAC per hour, you can estimate how long it takes to reach zero. If you stop drinking at a BAC of 0.08 (the legal limit for driving in every U.S. state except Utah, which uses 0.05), it would take about five and a half hours to fully clear. At a BAC of 0.15, which is possible after several drinks in a short window, you’re looking at roughly 10 hours.
This is why someone who drinks heavily in the evening can still be over the legal limit the next morning. Sleep doesn’t speed the process. Coffee doesn’t speed it. Cold showers don’t speed it. Your liver works at its own pace.
Factors That Change How Fast You Process Alcohol
Body Weight and Composition
The less you weigh, the more a given amount of alcohol affects your BAC. But weight alone doesn’t tell the whole story. Two people at the same weight can reach different BAC levels based on body fat percentage, because fat tissue doesn’t absorb alcohol the way water-rich tissue does. A higher body fat percentage means the alcohol concentrates in a smaller volume of body water, pushing BAC higher.
Sex
Women generally reach higher BAC levels than men after drinking the same amount. There are a few reasons for this. Women tend to carry a higher percentage of body fat and a lower percentage of body water, which concentrates alcohol more. Women also produce less of the stomach enzyme that begins breaking down alcohol before it reaches the bloodstream. Hormonal fluctuations matter too: BAC can run higher than usual right before menstruation, even at a person’s typical drinking amount.
Food
Drinking on an empty stomach lets alcohol absorb rapidly, producing a faster, higher peak BAC. Eating before or while you drink slows absorption and spreads the alcohol load out over time, giving your liver a better chance of keeping up.
Liver Health and Fatigue
Your liver is the bottleneck. Anything that reduces its efficiency, whether chronic liver disease, dehydration, or simple fatigue, can slow alcohol elimination. When you’re exhausted or dehydrated, your liver processes alcohol less effectively, and you experience a higher BAC than you otherwise would from the same number of drinks.
Why EtG Tests Have a Longer Window
EtG tests are common in legal, workplace, and treatment monitoring settings precisely because they look past the alcohol itself. Your body converts a small fraction of alcohol into ethyl glucuronide, which lingers in urine long after the alcohol is gone. After moderate drinking, EtG typically stays detectable for 24 to 48 hours. Heavy drinking can push that to 72 hours or beyond. Because of this sensitivity, EtG tests can sometimes flag exposure to alcohol in hand sanitizers or mouthwash, though the levels are usually distinguishable from actual drinking.
A Practical Timeline
Here’s a realistic picture of what happens after a night of moderate to heavy drinking (say, four to six drinks over a few hours for someone of average weight):
- 0 to 2 hours after your last drink: BAC is near its peak, likely somewhere between 0.06 and 0.12.
- 6 to 8 hours later: BAC is dropping steadily but may not yet be zero, especially at the higher end.
- 12 to 16 hours later: Blood and breath alcohol are likely undetectable for most people.
- 24 to 48 hours later: An EtG urine test could still come back positive.
- 48 to 80 hours later: EtG detection is still possible after heavier drinking episodes.
The one-drink-per-hour rule is a useful baseline, but it’s an average. Your actual clearance rate depends on your body, your liver, how much you ate, and how much you drank. When the timing matters, whether for a test, for driving, or for medication interactions, build in a wider margin than you think you need.