Your body clears alcohol at a steady rate of about one standard drink per hour. But “in your system” can mean different things depending on the test. A standard blood test can detect alcohol for up to 12 hours after your last drink, while a urine test that looks for alcohol byproducts can pick up traces for 48 to 72 hours or longer.
How Your Body Processes Alcohol
Your liver does the heavy lifting. It breaks alcohol down in two steps: first into a toxic byproduct called acetaldehyde (a known carcinogen), then quickly into acetate, which your body converts to carbon dioxide and water. The liver handles this at a remarkably fixed pace, roughly one standard drink per hour, and there’s no way to speed it up. Coffee, cold showers, and exercise don’t help. Time is the only thing that clears alcohol from your system.
A standard drink in the United States contains 14 grams of pure alcohol. That’s one 12-ounce beer, one 5-ounce glass of wine, or one 1.5-ounce shot of liquor. If you have four drinks in an evening, expect your body to need approximately four hours just to process the alcohol itself, not counting the time it takes to absorb and distribute it.
Detection Times by Test Type
Different tests look for different things, and their detection windows vary dramatically.
- Blood test: Detects alcohol for up to about 12 hours after your last drink. This is the most direct measurement of how much alcohol is currently in your bloodstream.
- Breathalyzer: Can detect alcohol on your breath for up to 24 hours, though 12 hours is more typical for moderate drinking. The window depends heavily on how much you drank.
- Urine test (standard): Similar to blood, roughly 12 hours for a basic screening.
- Urine test (EtG): This more sensitive test looks for a metabolic byproduct rather than alcohol itself. After a few drinks, it can detect this marker for up to 48 hours. Heavier drinking can push that window to 72 hours or longer.
- Hair test: Alcohol markers show up in hair strands for 3 to 6 months. It takes several weeks after drinking for the markers to appear, so hair tests reflect a pattern of use rather than a single episode. Most labs test the most recent 1.5 inches of hair growth.
What Affects How Fast You Clear Alcohol
While the one-drink-per-hour rule is a useful average, several factors shift the timeline in either direction. Body weight matters because alcohol distributes through body water, so a larger person dilutes the same amount of alcohol across more volume. Biological sex plays a role too: women generally have less body water and more body fat per pound than men, which means the same number of drinks produces a higher blood alcohol concentration.
Liver health is the single biggest variable. Chronic heavy drinking, liver disease, or hepatitis can significantly slow your liver’s ability to process alcohol. Age also matters, as enzyme activity tends to decline over time. Even genetic differences in the specific enzymes that break down alcohol vary between individuals and ethnic populations, making some people naturally faster or slower metabolizers.
How Food Changes the Timeline
Eating before or while drinking doesn’t change how fast your liver processes alcohol, but it does change how quickly alcohol reaches your bloodstream in the first place. Alcohol absorbs much faster on an empty stomach. A solid meal slows the rate at which your stomach empties its contents into the small intestine, where most absorption happens. This means your blood alcohol level peaks later and at a lower point when you’ve eaten.
Some research suggests food may also slightly increase the rate at which your body eliminates alcohol, though the primary effect is on absorption. In practical terms, drinking on a full stomach means you’ll feel the effects more gradually and your peak blood alcohol concentration will be lower than if you drank the same amount while fasting.
How Long Until You’re Legally Sober
The legal blood alcohol limit for driving is 0.08 grams per deciliter in most U.S. states (0.05 in Utah). What catches many people off guard is how long it takes to get back to zero. If you stop drinking at midnight with a blood alcohol concentration of 0.08, you won’t reach 0.00 until roughly 5:30 a.m., assuming the typical clearance rate. Heavier drinking pushes that timeline much further. A night of heavy drinking that puts you at 0.15 could mean you’re still over the legal limit well into the next morning.
It’s also worth knowing that you can feel completely sober while still having a measurable blood alcohol level. Your brain adapts to alcohol’s effects faster than your liver can clear it, creating a gap between how impaired you feel and how impaired you actually are. This is why morning-after impairment is a real and underestimated risk.