Alcohol leaves your system at a fairly predictable rate: your liver processes roughly one standard drink per hour. But “in your system” can mean different things depending on whether you’re talking about feeling sober, passing a breathalyzer, or clearing a urine or hair test. A single drink may be undetectable in your blood within a few hours, while a heavy night out can show up in urine for three days or in hair for months.
What Counts as One Drink
Your liver doesn’t care whether you’re drinking craft beer or tequila. What matters is how much pure alcohol you consumed. In the U.S., one standard drink 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 liquor at 40%. A strong IPA, a generous wine pour, or a double cocktail can easily count as two or more standard drinks, which changes your timeline significantly.
How Your Liver Processes Alcohol
Your liver does almost all the work. It breaks alcohol down in two steps. First, an enzyme converts alcohol into a toxic byproduct called acetaldehyde (a known carcinogen, though it doesn’t stick around long). A second enzyme quickly converts that into acetate, which your body then breaks down into water and carbon dioxide for easy elimination.
This process runs at a near-constant speed. Your liver can clear about one standard drink per hour, and there’s no reliable way to speed it up. Coffee, cold showers, and exercise don’t help your liver work faster. Time is the only thing that truly clears alcohol from your body.
Detection Windows by Test Type
Different tests look for different things and have very different detection windows:
- Blood: Up to 12 hours after drinking
- Breath: 12 to 24 hours, depending on how much you drank and individual factors
- Saliva: Up to 12 hours
- Urine (standard): 12 to 24 hours for light drinking, 72 hours or more after heavier use
- Urine (EtG test): Up to 48 hours after a few drinks, and sometimes 72 hours or longer after heavy drinking
- Hair: Up to 90 days, and in some cases 3 to 6 months
The EtG urine test deserves special attention because it doesn’t look for alcohol itself. It detects a byproduct your body creates when processing alcohol, which lingers in urine far longer than alcohol does. This is the test commonly used in court-ordered monitoring, probation, and workplace programs. After a few drinks, it can flag positive for two full days. After a heavy night, three days or more.
Hair tests work differently still. They detect markers deposited in the hair strand as it grows. Most labs test the 1.5 inches of hair closest to the scalp, which represents roughly 90 days of growth. In theory, markers could be detected in longer hair for even longer periods, but most people cut their hair often enough that 3 to 6 months is the practical maximum.
Why Timelines Vary From Person to Person
The “one drink per hour” rule is an average. Several biological factors push that number up or down.
Sex. Women generally reach higher blood alcohol levels than men after drinking the same amount, even at the same body weight. The primary reason is body composition: women typically carry a lower proportion of body water, and alcohol distributes mainly into water. Less water means the same amount of alcohol becomes more concentrated. There are also differences in enzyme activity between men and women that affect how quickly alcohol is broken down in the stomach and liver.
Age. As you get older, your lean body mass and total body water decrease while body fat increases. Since alcohol doesn’t distribute well into fat, older adults tend to reach higher blood alcohol concentrations from the same number of drinks they handled more easily when younger.
Body size and liver volume. Larger people with bigger livers can process alcohol faster in absolute terms (more grams per hour), though the rate per unit of liver tissue stays roughly the same.
Food. Eating before or while you drink has a major effect on how alcohol enters your bloodstream, though less effect on how fast your liver clears it. In one study, people who drank on a full stomach absorbed only about 66 to 71% of the alcohol that fasting subjects absorbed from the same amount. Their peak blood alcohol was substantially lower (roughly 30% less on average). Food slows the release of alcohol from your stomach into the small intestine, where most absorption happens. The practical result: drinking on a full stomach means less alcohol hits your bloodstream, so there’s less for your liver to clear.
How Many Drinks and How Long to Clear
A rough guide based on the one-drink-per-hour metabolism rate: if you have three standard drinks over the course of an evening, your body needs approximately three hours after your last drink to fully metabolize the alcohol, assuming you spaced them out. If you consumed them quickly, your BAC climbed higher and your liver still works at the same fixed pace, so clearance takes longer from that higher peak.
For heavier drinking, the math scales accordingly. Six drinks means roughly six hours of processing time from when you stop drinking. Someone who has eight or more drinks in an evening could still have alcohol in their blood well into the next afternoon. This is why people sometimes fail morning breathalyzers after a late night out. A breathalyzer can detect alcohol on your breath for up to 24 hours after drinking, and a night of heavy drinking that ends at 2 a.m. can easily leave detectable alcohol at 8 or 9 the next morning.
What Drinking Water Actually Does
Staying hydrated while drinking won’t help your liver clear alcohol any faster. The enzymatic process runs at its own pace regardless of how much water you consume. What hydration does help with is how you feel. Research shows that rehydrating can reduce some of the cognitive impairment associated with alcohol, particularly when your body is already fluid-depleted. So water may help you think more clearly and feel less awful the next morning, but it won’t make you pass a test sooner or get you sober faster.
Practical Timelines
If you’re wondering whether you’re safe to drive, the answer is simpler than the biology: count your drinks, count the hours since your last one, and add a buffer. Two drinks finishing at midnight means your blood alcohol is likely near zero by 2 a.m., but individual variation means it could take longer. Three or four drinks finishing at midnight could mean detectable alcohol until 4 or 5 a.m. Heavy drinking into the early morning hours can leave you impaired well past noon the next day.
If you’re facing a urine test, standard alcohol screening clears within about 24 hours for moderate drinking. EtG testing, however, requires two to three days of abstinence to reliably clear, and heavy drinking may need even longer. For hair testing, there is no short-term strategy: the markers are physically embedded in the strand as it grows and remain there until the hair is cut.