Hangover symptoms typically include headache, nausea, fatigue, thirst, muscle aches, sensitivity to light and sound, anxiety, irritability, dizziness, and difficulty concentrating. They begin once your blood alcohol level drops to or near zero, which for most people means the morning after a night of heavy drinking. Most hangovers resolve on their own, but they can make you feel miserable for anywhere from 12 to 24 hours.
The Full List of Symptoms
Hangovers affect nearly every system in your body. The most commonly reported symptoms are fatigue, weakness, thirst, headache, muscle aches, nausea, stomach pain, vertigo, sensitivity to light and sound, anxiety, irritability, sweating, and increased blood pressure. Researchers who developed a standardized scale for measuring hangover severity identified 47 distinct symptoms, eventually narrowing the most consistent ones down to 12 core experiences: fatigue, clumsiness, dizziness, apathy, sweating, stomach problems, concentration difficulties, and several others that overlap with what most people intuitively recognize as a hangover.
Not everyone gets the same mix. Some people are hit hardest by the headache and light sensitivity, while others mainly deal with nausea and stomach pain. Your particular symptom profile depends on how much you drank, what you drank, how well you slept, and your individual biology.
Physical Symptoms
The physical side of a hangover tends to dominate the experience. Headache is the hallmark, often throbbing and worsened by movement. Nausea and stomach pain are extremely common because alcohol irritates the lining of your stomach and increases acid production. Some people also experience vomiting or diarrhea.
Thirst and dry mouth come from alcohol’s diuretic effect, which causes you to lose more fluid than you take in. But dehydration alone doesn’t explain the full picture. Your body is also dealing with an inflammatory immune response. During a hangover, your immune system ramps up production of certain signaling molecules that promote inflammation. Research has shown that levels of several of these inflammatory markers rise significantly during the hangover state compared to normal conditions, and this immune disruption is thought to directly contribute to the nausea, headache, fatigue, and diarrhea that define the experience.
Muscle aches, sweating, increased blood pressure, and a racing heart round out the physical symptoms. Sensitivity to light and sound can make even normal environments feel overwhelming, which is why many people instinctively retreat to a dark, quiet room.
Mental and Emotional Symptoms
The cognitive effects of a hangover are real and measurable, not just “feeling off.” You may struggle to concentrate, have difficulty retaining new information, or find it hard to plan and organize tasks. These are functions controlled by the front part of your brain, which is particularly sensitive to alcohol’s aftereffects. Reaction times slow down, and clumsiness increases, which is one reason hangovers meaningfully impair driving ability even when you’re technically sober.
Emotionally, anxiety is one of the most common hangover symptoms, sometimes called “hangxiety.” Irritability, mood swings, and a general feeling of apathy or low motivation often accompany it. These mood effects stem partly from alcohol’s disruption of brain chemistry as your nervous system rebounds from its depressant effects, and partly from poor sleep and physical discomfort compounding each other.
How Sleep Disruption Makes It Worse
Alcohol helps you fall asleep faster, but the quality of that sleep is significantly worse. After drinking, your brain spends less time in the deep, restorative sleep stages, particularly REM sleep. You’re also more prone to waking up during the night, even if you don’t remember it the next day. According to researchers at Baylor College of Medicine, this means you’re fighting two battles the next morning: the direct effects of alcohol on your body and the effects of a fragmented, low-quality night of sleep.
A shorter or more disrupted night of sleep contributes to worse concentration, slower thinking, and greater overall hangover severity. This is why sleeping in after drinking sometimes helps, and why hangovers feel worse when you had to wake up early.
When Symptoms Start and How Long They Last
Hangover symptoms begin as your blood alcohol concentration drops toward zero. For most people, this means symptoms are at their worst in the morning, several hours after you stopped drinking. The timeline varies depending on how much you consumed. Someone who stopped drinking at midnight might feel worst around 7 or 8 a.m., while someone who drank until 3 a.m. might not peak until midday.
Most hangovers resolve within 24 hours, though severe ones from very heavy drinking can linger into a second day. The headache and nausea usually fade first, while fatigue and mood effects tend to be the last to go.
Why Some Drinks Cause Worse Hangovers
The type of alcohol you drink matters. Darker spirits like bourbon, whiskey, and brandy tend to produce worse hangovers than lighter options like vodka, even at the same total amount of alcohol consumed. The difference comes down to congeners, which are byproducts of the fermentation and aging process. Darker drinks contain far more of these compounds. One study found that hangover severity scores were significantly higher after bourbon compared to vodka when participants reached the same blood alcohol level.
Methanol is considered one of the most significant congeners contributing to hangovers. Your body breaks it down into toxic byproducts more slowly than it processes regular alcohol, which extends and worsens symptoms. Interestingly, though, the type of drink didn’t affect cognitive performance. Whether participants drank bourbon or vodka, their scores on thinking and coordination tests were equally impaired the next day. So while you might feel subjectively worse after dark liquor, your brain takes the same hit regardless.
Some People Don’t Get Hangovers at All
About 5% of heavy drinkers report never experiencing a hangover in their entire lives, even at blood alcohol levels well above the legal driving limit. This holds roughly equally for men and women. Researchers have confirmed this isn’t just a matter of people forgetting or minimizing their symptoms. A small subset of the population genuinely appears to be hangover-resistant.
The reasons aren’t fully understood, but genetics likely play a major role, particularly variations in how efficiently your liver processes alcohol and its toxic byproducts. This doesn’t mean these individuals escape alcohol’s health effects. The damage to organs and the brain happens whether or not you feel hungover the next morning.
What’s Actually Happening in Your Body
A hangover isn’t caused by any single mechanism. It’s the result of several overlapping processes. Alcohol is broken down into a toxic intermediate compound before being converted into something harmless. When you drink faster than your liver can keep up, that toxic intermediate accumulates and damages tissues. At the same time, alcohol triggers an inflammatory immune response, with your body releasing signaling molecules normally associated with fighting infection. This misfired immune activation produces many of the symptoms that feel like being sick: fatigue, nausea, headache, and body aches.
Dehydration and electrolyte imbalance contribute to thirst, dizziness, and lightheadedness. Alcohol also irritates the stomach lining directly, which drives nausea and stomach pain independent of what’s happening elsewhere in the body. And the sleep disruption layered on top of all this means your brain hasn’t had the recovery time it needs, amplifying every other symptom. It’s this combination of immune activation, toxic byproducts, dehydration, gut irritation, and poor sleep that makes hangovers feel so comprehensively awful.