The effects of alcohol typically last anywhere from a few hours to a full day, depending on how much you drink, your body size, and several other personal factors. Your body clears alcohol at a fixed rate of about 0.015% BAC per hour, which means a single standard drink takes roughly one to two hours to fully metabolize, while a night of heavy drinking can leave you impaired well into the next day.
How Fast Your Body Processes Alcohol
Your liver does nearly all the work of breaking down alcohol. It converts ethanol into a toxic byproduct called acetaldehyde, then quickly breaks that down into acetate, which eventually leaves the body as carbon dioxide and water. This process runs at a remarkably consistent pace: about 0.015% BAC reduction per hour, regardless of how much you’ve had. That rate doesn’t speed up with coffee, cold showers, or food after the fact.
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. Each standard drink raises most people’s BAC by roughly 0.02% to 0.03%, though this varies with body size. At the fixed clearance rate of 0.015% per hour, a single drink takes about one to two hours to leave your system. Four drinks might put you around 0.08% to 0.10%, meaning you’d need six to seven hours just to get back to zero.
What Impairment Looks Like at Each Level
Alcohol’s effects aren’t all-or-nothing. They escalate in a predictable pattern as BAC rises, and they fade in reverse as your liver works through the backlog.
- 0.02% BAC (about one drink): Slight relaxation, mild warmth, subtle changes in mood and judgment. You may have trouble tracking moving objects.
- 0.05% BAC (two to three drinks): Lowered alertness, reduced coordination, exaggerated behavior. Small-muscle control starts to slip, making it harder to focus your eyes.
- 0.08% BAC (three to four drinks): This is the legal driving limit in most U.S. states. Balance, speech, vision, and reaction time are all noticeably impaired. Short-term memory and judgment take a real hit.
- 0.10% BAC: Slurred speech, slowed thinking, clear deterioration of reaction time.
- 0.15% BAC and above: Significant loss of balance and muscle control. Vomiting is common unless you’ve built up a high tolerance.
If you reach 0.10% BAC, it will take roughly six to seven hours to return to zero. During most of that time, you’re still impaired to some degree, even if you feel “fine” after a few hours. Judgment and reaction time are among the last functions to fully recover.
Why It Lasts Longer for Some People
The 0.015%-per-hour clearance rate is an average. Several factors push your actual timeline shorter or longer.
Biological sex plays a significant role. Men produce about 40% more of the enzyme that breaks down alcohol than women do. Women also tend to carry a higher percentage of body fat, and since alcohol doesn’t distribute into fat tissue, the same number of drinks produces a higher concentration in a smaller woman’s lean tissue. The result: women typically reach higher BAC levels faster and stay impaired longer from the same amount of alcohol.
Body size and composition matter beyond sex differences. A person who weighs 130 pounds will hit a higher BAC from two drinks than someone who weighs 200 pounds, simply because there’s less lean body mass to distribute the alcohol through.
Food in your stomach doesn’t change your metabolism rate, but it significantly changes how quickly alcohol hits your bloodstream. Drinking on an empty stomach causes BAC to spike faster and higher. A full meal eaten close to the time you drink lowers peak BAC, which means you feel less impaired and your body finishes processing the alcohol sooner. The type of food (protein, fat, or carbs) doesn’t seem to matter much. What matters is the size of the meal and how recently you ate it.
Hydration is another factor. Drinking 250 mL of an alcoholic beverage causes your body to expel 800 to 1,000 mL of fluid, meaning alcohol is a powerful diuretic. This dehydration doesn’t change how fast your liver works, but it intensifies symptoms like headache and fatigue both during and after intoxication.
How Long Alcohol Shows Up on Tests
Even after you feel completely sober, alcohol or its byproducts can still be detected in your body. The window depends on the test:
- Breath: A breathalyzer can detect alcohol for up to 24 hours after drinking, though 12 hours is more typical for moderate amounts.
- Blood: Blood tests pick up alcohol for up to 12 hours.
- Urine: Standard urine tests detect alcohol for 12 to 24 hours, but specialized tests that look for metabolic byproducts can flag drinking up to 5 days later.
- Hair: A hair follicle test can detect alcohol for up to 90 days.
How Long a Hangover Lasts
A hangover is a separate phase that begins right around the time your BAC drops back to zero. It’s not residual intoxication. It’s your body’s inflammatory and dehydration response to the alcohol that’s already been processed. The average hangover lasts about 18 hours from the time you stop drinking, though most people experience it as roughly 12 hours of misery from the time they wake up. For most drinkers, hangover duration falls between 14 and 23 hours total.
Symptoms tend to build gradually and peak around 14 hours after your last drink. If you stopped drinking at midnight, that peak hits around 2 p.m. the following day. Headache, nausea, fatigue, sensitivity to light, and difficulty concentrating are the most common complaints. Cognitive function, particularly memory and attention, can remain below normal throughout the hangover period even though no alcohol remains in your blood.
A Realistic Timeline for a Night Out
To put all of this together: say you have four drinks between 8 p.m. and midnight. Your BAC likely peaks somewhere around 0.07% to 0.09%. At the standard clearance rate, you won’t reach 0.00% until roughly 5 to 7 a.m. If you drank more heavily and reached 0.15%, you’re looking at 10 hours of metabolism, meaning you could still be legally impaired at noon the next day.
After your BAC hits zero, the hangover clock starts. If the drinking was heavy enough to trigger one, expect symptoms to last through most of the following day, peaking in the early-to-mid afternoon. All told, a night of heavy drinking can produce noticeable effects for 24 hours or more, from the first sip to the tail end of the hangover.