A typical hangover lasts up to 24 hours, though some can stretch longer depending on how much you drank, what you drank, and how your body processes alcohol. Symptoms peak once your blood alcohol concentration drops back to zero, which for most people means the worst hits the morning after a night of heavy drinking. From that peak, you’re generally looking at a full day before you feel like yourself again.
What the Timeline Looks Like
Hangovers don’t start while you’re still drunk. They begin as alcohol leaves your system, typically kicking in several hours after your last drink. If you stop drinking at midnight, you might wake up at 6 or 7 a.m. feeling fine, only to feel progressively worse through the morning as your blood alcohol level continues to fall. The NIAAA notes that symptoms peak right around the point when your BAC hits zero, and they can persist for 24 hours or longer after that.
The early hours tend to bring nausea, headache, and sensitivity to light or sound. As the day progresses, many people notice those sharp symptoms fade but get replaced by a lingering fatigue, brain fog, and general sluggishness that can hang on well into the evening. If you drank heavily enough, or if other factors are working against you, that second wave of exhaustion can bleed into the following day.
Why Some Hangovers Last Longer Than Others
The biggest factor is simply how much you drank. More alcohol means more of a toxic byproduct called acetaldehyde that your liver has to break down. Your liver handles this in two steps: first it converts alcohol into acetaldehyde (which causes many of the worst hangover symptoms), then it converts acetaldehyde into a harmless substance your body can eliminate. When you overwhelm that second step by drinking heavily, acetaldehyde builds up and sticks around longer, dragging out the misery.
What you drank matters too. Darker spirits like bourbon, whiskey, and red wine contain higher levels of congeners, the chemical compounds that give drinks their color and flavor. Research published in Alcohol and Alcoholism found that high-congener drinks produce more severe hangovers, and that it takes fewer of them to trigger symptoms in the first place. Clear liquors like vodka and gin have fewer congeners and tend to produce milder aftereffects, all else being equal.
Dehydration plays a role as well. Alcohol suppresses a hormone that helps your kidneys retain water, so you lose fluid faster than normal while drinking. That fluid loss contributes to headache, dizziness, and dry mouth. Whether you ate before drinking also matters. Alcohol on an empty stomach can trigger a drop in blood sugar that causes fatigue, shakiness, and a foggy feeling that can linger for hours. The NHS notes that alcohol-related low blood sugar can occur many hours after drinking, which helps explain why some people feel wiped out well into the next day even after the nausea has passed.
The Anxiety That Comes With It
If you’ve ever felt an unexplained wave of dread or nervousness the day after drinking, you’re experiencing what’s sometimes called “hangxiety.” It has a straightforward biological cause. Alcohol initially boosts the activity of your brain’s main calming chemical while suppressing excitatory signals, which is why drinking feels relaxing. As alcohol clears your system, the balance flips: calming activity drops below baseline while excitatory signals surge. The result is a state of heightened brain activity that feels like anxiety, restlessness, or a racing mind.
This rebound effect typically peaks alongside other hangover symptoms and fades over the course of the day. For people who already deal with anxiety, it can feel more intense and last longer. It’s one of the less obvious hangover symptoms, and people often don’t connect it to drinking because it doesn’t feel like a “physical” symptom.
Genetics and the Enzyme That Matters Most
Your genes have a significant influence on how long your hangovers last. The key player is the enzyme responsible for clearing acetaldehyde from your body. Roughly 8% of the world’s population, and up to 30 to 40% of people of East Asian descent, carry a genetic variant that makes this enzyme far less effective. People with this variant accumulate acetaldehyde much faster and struggle to eliminate it, which is why they often experience facial flushing, rapid heartbeat, nausea, and headaches even after small amounts of alcohol.
If you’ve always noticed that your hangovers seem disproportionately bad compared to friends who drank the same amount, this enzyme difference is a likely explanation. It’s not about tolerance or toughness. It’s a measurable difference in how quickly your body can neutralize a toxic compound.
Does Age Make Hangovers Worse?
The common belief is that hangovers get worse as you get older, and there are real biological reasons to expect that. Your liver becomes less efficient at producing the enzymes that break down alcohol and its byproducts. Older adults also carry less water in their bodies, which means the same number of drinks produces a higher blood alcohol concentration. A slower overall metabolism means alcohol and its toxic byproducts linger in your system longer.
That said, the science is surprisingly mixed. One 2021 study actually found that hangover severity decreased with age, with older participants reporting less intense symptoms. One possible explanation is that older adults tend to drink less and pace themselves more carefully, which offsets the metabolic disadvantage. The takeaway is that your body does become less efficient at processing alcohol over time, but your drinking habits can matter just as much as your biology.
When a Hangover Takes Longer Than a Day
If your symptoms are still going strong past the 24-hour mark, a few things could be happening. You may have drunk significantly more than you realized, especially if drinks were mixed or poured generously. Sleep disruption is another factor: alcohol fragments your sleep architecture, reducing the restorative deep sleep your body needs to recover. Even if you slept for eight hours, the quality of that sleep was poor, and the fatigue compounds on top of the hangover itself.
A “two-day hangover” is usually a combination of genuine hangover symptoms on day one followed by sleep debt, dehydration, and depleted energy stores on day two. The headache and nausea are gone, but you still feel drained. Eating regular meals, hydrating steadily, and getting a proper night of sleep will typically resolve what’s left.
Symptoms that persist beyond 48 hours, or that include confusion, repeated vomiting, seizures, or slow breathing, aren’t a hangover. Those are signs of alcohol poisoning or withdrawal, which are distinct medical situations.