Alcohol is typically detectable in your blood for up to 12 hours after your last drink, but specialized tests can find traces for days or even months. The exact window depends on which type of test is used and how much you drank. Your body clears alcohol at a fixed rate of about 0.015 blood alcohol concentration (BAC) per hour, which means a single drink takes roughly one to two hours to fully metabolize, while a heavy night of drinking could take well into the next day.
Detection Windows by Test Type
Different tests look for different things. Some measure alcohol itself, while others detect byproducts your body creates as it breaks alcohol down. Here’s how long each method can pick up evidence of drinking:
- Blood: Up to 12 hours for a standard test. A specialized blood test that measures a byproduct called PEth can detect moderate or heavy drinking for up to four weeks.
- Breath: 12 to 24 hours, depending on how much you drank and your individual metabolism.
- Urine: A standard urine test picks up alcohol for 12 to 24 hours. After heavier drinking, that extends to 72 hours or more. An EtG urine test, which looks for a metabolic byproduct rather than alcohol itself, can return a positive result up to five days later, though its accuracy drops significantly after the first 24 hours.
- Saliva: Up to 12 hours.
- Hair: One to six months, with 90 days being the most common testing window.
How Your Body Processes Alcohol
Your liver does the heavy lifting. It produces an enzyme that breaks down alcohol at a steady rate of about 0.015 BAC per hour. That rate is essentially fixed. You can’t speed it up with coffee, water, food, or cold showers once the alcohol is already in your bloodstream.
To put that in practical terms: if your BAC reaches 0.08 (the legal driving limit in most U.S. states), it will take roughly five and a half hours for your body to clear all the alcohol. A BAC of 0.15, which might result from a night of heavy drinking, would take about 10 hours to reach zero. One standard drink in the U.S. contains about 14 grams of pure alcohol, whether that’s a 12-ounce beer, a 5-ounce glass of wine, or a 1.5-ounce shot of liquor.
What Affects How Long It Stays
Even though the liver’s processing rate is relatively constant, several factors influence how high your BAC climbs in the first place, and therefore how long it takes to come back down.
Body size matters because alcohol distributes through body water. A larger person has more volume to dilute the same number of drinks, resulting in a lower peak BAC. Sex plays a role too: women generally reach a higher BAC than men after the same amount of alcohol, partly because of differences in body composition and the enzymes involved in breaking alcohol down.
Food has a significant effect on absorption. Drinking on an empty stomach lets nearly all the alcohol reach your bloodstream quickly. Eating a meal before drinking can reduce the amount of alcohol your body actually absorbs by roughly 30%, according to research that measured breath alcohol levels in people who drank after fasting versus after eating. That lower peak means less total time before your system is clear.
Age changes the picture in a less obvious way. Younger adults (under 24) tend to be less sensitive to the sedating effects of alcohol, which can lead them to drink more before feeling impaired. Older adults often have slower metabolisms and less body water, meaning the same number of drinks produces a higher, longer-lasting BAC. Liver health is another factor: any condition that reduces liver function, from fatty liver disease to hepatitis, slows the rate at which your body can process alcohol.
EtG and PEth: The Tests That Look Further Back
If you’re concerned about a test catching drinking from several days ago, you’re likely dealing with one of two specialized tests. The EtG urine test is the most common in workplace and court-ordered screening. It detects a byproduct your body produces when it metabolizes alcohol, not the alcohol itself. That’s why it has such a long detection window, up to five days in some cases. However, results from this test are typically interpreted on a scale: a low positive suggests light drinking within the past 24 to 36 hours, while a higher reading suggests heavier or more recent use.
The PEth blood test works differently. It measures a substance that forms in red blood cell membranes when alcohol is present. Because red blood cells live for weeks, PEth can indicate drinking patterns over the previous month. It’s best at detecting moderate to heavy use over that four-week window rather than a single drink days ago.
Hair follicle tests have the longest lookback period. Alcohol byproducts get deposited in hair as it grows, creating a timeline that can stretch back six months. These tests are less common for routine screening but are sometimes used in legal or custody situations where a longer drinking history is relevant.
How Many Drinks Shifts the Timeline
The number of drinks you’ve had is the single biggest variable in how long alcohol stays detectable. One beer at dinner will likely clear your blood within a couple of hours and be undetectable on a standard urine test by the next morning. Five or six drinks over an evening could keep your BAC elevated for eight to ten hours and leave enough metabolic evidence for an EtG test to detect for two to three days.
Binge drinking extends every detection window. After a night of very heavy consumption, standard urine tests can still pick up alcohol at 72 hours or beyond. EtG levels remain elevated even longer. And because your liver can only work at its fixed rate, stacking drinks faster than one per hour simply builds a backlog that takes proportionally longer to clear.