Most hangovers last between 8 and 24 hours, with symptoms peaking right around the time your body finishes processing all the alcohol in your system. A mild hangover after a few drinks might clear up by lunchtime, while a severe one after a heavy night can drag well into the following evening. The exact timeline depends on how much you drank, what you drank, your age, and your individual biology.
When Symptoms Peak and When They Fade
Hangover symptoms hit their worst point when your blood alcohol concentration drops back to zero. For most people, the body processes roughly one standard drink per hour, so if you stopped drinking at midnight after eight drinks, your blood alcohol might not reach zero until 8 a.m. or later. That’s when the headache, nausea, and fatigue tend to be at their most intense.
From that peak, you’re looking at a gradual decline over the next several hours. A moderate hangover typically resolves within 12 hours of waking. A severe one, especially after a long night of heavy drinking, can produce symptoms that linger for a full 24 hours or more. Cognitive effects like poor concentration, sluggish memory, and difficulty staying on task can persist even after the physical discomfort fades.
What’s Actually Happening in Your Body
A hangover isn’t just “dehydration,” though that’s part of it. When your liver breaks down alcohol, it first converts it into a toxic compound called acetaldehyde. That process generates harmful molecules called free radicals, which overwhelm your body’s natural defenses and trigger inflammation. Your immune system responds to the damage the same way it would respond to an infection: by releasing inflammatory signaling molecules. That’s why a bad hangover can feel eerily similar to coming down with the flu.
The slower your body clears alcohol from your system, the longer these inflammatory processes run. People who metabolize alcohol slowly end up with more of it sitting in their system during the second half of the night and into the morning, which means more oxidative stress, a stronger inflammatory response, and a worse hangover overall.
Alcohol also acts as a diuretic. Consuming roughly four drinks causes your body to flush out 600 to 1,000 milliliters of water (up to a full quart) over several hours. That fluid loss contributes to thirst, dizziness, weakness, and dry mouth. On top of that, alcohol can lower blood sugar, which adds to the shakiness and fatigue many people feel the morning after.
Why Your Sleep Feels Useless
Even if you slept for eight hours after drinking, you probably didn’t get eight hours of real rest. Alcohol helps you fall asleep faster, but it wrecks the second half of your night. Once your body starts metabolizing the alcohol, sleep becomes fragmented. You spend more time in light, shallow sleep and wake up more often. The result is that you start the next day already running a sleep deficit, which compounds every other hangover symptom and makes fatigue one of the longest-lasting effects.
Factors That Make It Last Longer
Several things can stretch a hangover well beyond the typical window.
- What you drank: Dark-colored spirits like bourbon, whiskey, and red wine contain higher levels of congeners, chemical byproducts of fermentation. Studies comparing bourbon drinkers to vodka drinkers found that bourbon produced significantly worse hangover symptoms, thanks to its higher congener content. Lighter-colored drinks like vodka and gin tend to cause milder hangovers at the same alcohol volume.
- How much you drank: More alcohol means more acetaldehyde, more inflammation, and a longer processing time. The math is straightforward: double the drinks, roughly double the hours your body needs to clear everything out.
- Your age: Alcohol metabolism slows as you get older. The enzymes your body uses to break down alcohol become less efficient over time, which is why the same amount of drinking that barely bothered you at 22 can flatten you at 40.
- Your genetics: Not everyone produces the same levels of the enzymes needed to process alcohol. Some people, particularly those of East Asian descent, carry genetic variants that cause acetaldehyde to build up faster, leading to more intense and longer-lasting symptoms.
What Actually Helps (and What Doesn’t)
Time is the single most effective hangover cure. Your body needs to finish clearing the inflammatory byproducts of alcohol metabolism, and no pill or drink can speed that up in any meaningful way.
One of the most persistent beliefs is that drinking lots of water will cure a hangover. Research tells a different story. A study examining water consumption during and after drinking found that it had only a modest effect on preventing next-day hangovers, and drinking water during a hangover did not reduce symptom severity. Dehydration and hangovers happen simultaneously after drinking, but they appear to be largely independent processes. Rehydrating will fix the dehydration symptoms (thirst, dry mouth, dizziness) but won’t touch the underlying inflammation driving the headache, nausea, and fatigue.
That said, a few things can take the edge off while you wait it out. Bland, carbohydrate-rich foods like toast or crackers help stabilize blood sugar, which can relieve some of the shakiness and nausea. Fruit or fruit juice provides fructose, which some evidence suggests may reduce hangover intensity modestly. And simply getting more sleep, if your schedule allows it, helps counteract the poor-quality rest from the night before.
Over-the-counter pain relievers can address the headache, but be cautious with anything containing acetaminophen. Your liver is already working overtime processing alcohol byproducts, and acetaminophen adds to that burden. Ibuprofen or aspirin are generally easier on the liver, though both can irritate a stomach that’s already inflamed from drinking.
The Cognitive Hangover Lasts Longer Than You Think
Even after the headache fades and your stomach settles, your brain may not be back to normal. Research on hangover-related cognitive impairment shows deficits in attention, memory, and information processing that persist throughout the hangover state. People in a hungover state also perform worse on tasks that require remembering to do something in the future, like keeping appointments or following through on plans. These mental effects can linger for the full 24-hour window, meaning your productivity and decision-making may be compromised well after you physically “feel fine.”