Alcohol leaves your body at a fixed rate of about 0.015 BAC per hour, which works out to roughly one standard drink every 60 to 90 minutes. But “how long it stays in your system” depends on what you mean: whether you’re asking about impairment, a breathalyzer, a urine test, or a hair test. Each has a very different detection window, ranging from hours to months.
How Your Body Processes Alcohol
Your liver does the heavy lifting. It uses an enzyme to convert alcohol into a toxic byproduct called acetaldehyde (a known carcinogen), then quickly converts that into acetate, which breaks down into water and carbon dioxide that your body easily eliminates. This process is efficient but not fast. Your liver can only handle so much at once, which is why BAC drops at a near-constant rate regardless of how much you drank. You can’t speed it up with coffee, water, or food after the fact.
A standard drink in the United States contains about 14 grams of pure alcohol. That’s 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of distilled spirits. If you have three standard drinks and reach a BAC of around 0.045, it would take roughly three hours for your BAC to return to zero.
Detection Windows by Test Type
Different tests pick up alcohol or its byproducts for different lengths of time:
- Blood and breath: Alcohol is detectable for roughly 12 to 24 hours after your last drink, depending on how much you consumed. A standard breathalyzer mirrors your blood alcohol level in real time.
- Saliva: Up to 24 hours.
- Standard urine test: Alcohol itself clears from urine within about 12 hours. However, a more sensitive urine test looks for a metabolite called EtG (a compound your body produces as it breaks down alcohol). After a few drinks, EtG can show up in urine for 48 hours and sometimes 72 hours or longer after heavier drinking.
- Hair follicle test: Alcohol markers can appear in a hair strand for 1 to 6 months. Hair tests aren’t used to detect recent drinking; they’re designed to identify patterns of use over time.
If you’re facing a workplace or legal test, the type of test matters enormously. An EtG urine test is far more sensitive than a standard breathalyzer, and a hair test operates on an entirely different timescale.
Factors That Change How Fast You Clear Alcohol
The 0.015-per-hour rate is an average. Several things shift it up or down for any given person.
Biological sex. Women generally reach higher blood alcohol levels than men after the same number of drinks, even at the same body weight. Women tend to have less body water and different enzyme activity, which means alcohol stays more concentrated in the bloodstream for longer. Health guidelines reflect this: thresholds for liver risk start at lower intake levels for women (roughly 20 grams per day) compared to men (roughly 30 grams per day).
Body weight and composition. A larger body with more water volume dilutes alcohol more effectively, leading to a lower peak BAC from the same number of drinks. But weight alone doesn’t tell the whole story. Two people at the same weight but different body fat percentages will metabolize alcohol differently, because fat tissue doesn’t absorb alcohol the way lean tissue does.
Liver health. This is a major variable that people often overlook. Fatty liver disease, now estimated to affect 30% to 40% of the general adult population (with higher rates among those with obesity or diabetes), makes the liver more vulnerable to alcohol’s toxic effects. People with this condition can experience greater harm from alcohol even at low doses, and their ability to process it efficiently may be compromised.
Age. Liver enzyme activity tends to decline with age, which generally means slower metabolism of alcohol. Older adults also tend to have less body water, contributing to higher BAC from the same intake.
How Food Changes the Equation
Eating before you drink has a significant effect on how alcohol moves through your body, though not in the way most people assume. Food doesn’t help you “sober up.” What it does is slow the rate at which alcohol enters your bloodstream in the first place.
Research comparing fasting and fed states found that people who drank on an empty stomach reached peak breath alcohol concentrations around 30.5 units on average, while those who ate a full meal beforehand peaked at only 21.4, roughly 30% lower. The effect on total absorption was even more striking: after a meal, the body only absorbed about 66% to 71% of the expected alcohol, compared to nearly 100% on an empty stomach. That’s a massive difference from the same number of drinks.
A snack, by contrast, did very little. People who had a light snack before drinking absorbed almost as much alcohol as those who fasted. The protective effect comes from a substantial meal, not a handful of crackers.
Alcohol and Breast Milk
Alcohol levels in breast milk closely track blood alcohol levels, peaking about 30 to 60 minutes after a drink. The general guideline is to allow about 2 hours per standard drink before nursing. So if you had two glasses of wine, you’d wait roughly four hours. This isn’t about the milk “holding” alcohol. As your blood alcohol drops, your milk alcohol drops with it. There’s no need to pump and dump; you just need to wait for the alcohol to clear.
A Rough Timeline for Common Scenarios
Putting it all together, here’s what clearance looks like for a few typical situations, assuming average metabolism:
- 1 standard drink: BAC returns to zero in about 1 to 1.5 hours. Undetectable on breath or blood within a few hours. Could still show on an EtG urine test for up to 48 hours.
- 3 standard drinks: BAC takes roughly 3 to 4 hours to reach zero. Breath and blood tests may detect alcohol for up to 12 hours depending on timing.
- Heavy drinking (6+ drinks): BAC may not reach zero for 8 to 10 hours or more. EtG could remain positive for 72 hours or longer.
These are estimates for an average-weight adult with normal liver function. Your personal timeline could be shorter or longer based on the factors above. The one thing you can’t change is the fundamental rate: your liver processes alcohol at its own pace, and no remedy, supplement, or trick will make it go faster.