Alcohol leaves your bloodstream at a fixed rate of about 0.015% blood alcohol concentration (BAC) per hour, regardless of your size or sex. For most people, one standard drink clears the blood in roughly one to two hours. But “your system” is broader than your bloodstream. Depending on the type of test, alcohol or its byproducts can be detected anywhere from 12 hours to 3 days after your last drink.
How Your Body Breaks Down Alcohol
Your liver does the heavy lifting. It processes alcohol in two steps using two enzymes. The first enzyme converts alcohol into a toxic compound called acetaldehyde, which is a known carcinogen. The second enzyme quickly breaks acetaldehyde down into acetate, a much less harmful substance. Acetate is then converted into water and carbon dioxide, which your body eliminates easily through breathing and urination.
This process is remarkably consistent. Your liver clears alcohol at about 0.015% BAC per hour, and you can’t speed it up. Coffee, cold showers, and exercise don’t help. If your BAC is 0.08% (the legal driving limit in most U.S. states), it will take roughly five and a half hours to reach 0.00%.
Detection Windows by Test Type
Different tests look for different things, and that changes how long alcohol is traceable.
- Blood and breath tests: These measure alcohol itself and are reliable for about 12 hours after your last drink. Breathalyzers and blood draws are most commonly used in legal and emergency settings.
- Saliva tests: Alcohol can be detected in saliva for up to 24 hours after drinking.
- Standard urine tests: A basic urine screen picks up alcohol for roughly 12 to 24 hours.
- EtG urine tests: These don’t look for alcohol directly. They detect a byproduct called ethyl glucuronide that your body produces when processing alcohol. After a few drinks, EtG can show up in urine for up to 48 hours. With heavier drinking, it can remain detectable for 72 hours or longer. This is the test used in most court-ordered, workplace, and treatment monitoring programs.
- Hair tests: Alcohol byproducts can be found in hair for up to 90 days, though hair testing for alcohol is less common and typically used in specific legal or custody situations.
What Changes How Fast You Feel Sober
While the liver’s clearance rate is fixed, several factors affect how high your BAC climbs in the first place, which determines how long it takes to come back down.
Food in Your Stomach
Eating before or while you drink makes a significant difference. Research comparing fasted and fed drinkers found that people who ate a meal before drinking absorbed only about 66 to 71% of the alcohol compared to those who drank on an empty stomach. Peak BAC was also substantially lower: fasting drinkers hit an average peak nearly 50% higher than those who had eaten. In practical terms, the same three drinks will affect you far more at happy hour on an empty stomach than over dinner.
Body Size and Composition
Larger people generally reach a lower BAC from the same amount of alcohol because there’s more body water to dilute it. Women typically reach a higher BAC than men after consuming the same amount, even at the same body weight. This is partly because women tend to have a higher ratio of body fat to water, concentrating the alcohol in a smaller volume of fluid.
Age
Young adults under 24 are less sensitive to some of alcohol’s early warning signs, like sedation and loss of coordination, which can lead them to drink more before feeling impaired. They are, however, more vulnerable to alcohol’s effects on memory. Older adults often feel the effects of alcohol more strongly because body water content decreases with age.
Does Liver Damage Slow Alcohol Processing?
You might assume that someone with liver disease would process alcohol more slowly. The research tells a different story. Studies comparing people with cirrhosis to those with healthy livers found no compelling evidence that alcohol clearance is significantly slower in cirrhotic patients. The rate of alcohol disappearance from blood in healthy subjects falls between 9 and 20 mg/dL per hour, and the range in people with cirrhosis is similar. That said, a damaged liver is far more vulnerable to additional harm from each drink, even if it clears alcohol at a normal pace.
Practical Timelines for Common Scenarios
Here’s a rough guide based on the 0.015% per hour clearance rate. These assume average-sized adults who aren’t drinking on a completely empty stomach.
- 1 to 2 standard drinks: Alcohol clears the bloodstream in about 2 to 3 hours. An EtG urine test could still detect it for up to 24 hours.
- 3 to 4 standard drinks: Blood alcohol returns to zero in roughly 4 to 6 hours. EtG may be positive for up to 48 hours.
- A heavy night of drinking (6+ drinks): You could still have measurable blood alcohol 8 to 12 hours later, meaning you may still be legally impaired the next morning. EtG can remain detectable for 72 hours or more.
A “standard drink” is 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of distilled spirits. Many cocktails and craft beers contain significantly more alcohol than one standard drink, so the actual number of drinks you’ve had is often higher than the number of glasses.
Why You Might Still Feel Off After Alcohol Clears
Hangover symptoms like headache, nausea, and fatigue can persist well after your BAC hits zero. This is partly because acetaldehyde, the toxic intermediate your liver produces while breaking down alcohol, causes inflammation and oxidative stress even during its brief existence. Dehydration, disrupted sleep, and irritation of your stomach lining also contribute. Feeling hungover doesn’t mean alcohol is still in your system, but it does mean your body is still recovering from its effects.