Being hungover means you’re experiencing a set of unpleasant physical and mental symptoms that follow a session of heavy drinking. These symptoms peak once your body has fully processed the alcohol, typically the morning after, and can last up to 24 hours or longer. A hangover isn’t just “still being drunk.” It’s your body reacting to the damage alcohol and its byproducts leave behind.
Common Hangover Symptoms
The word “hungover” describes a recognizable cluster of symptoms: headache, nausea, fatigue, dizziness, thirst, and difficulty concentrating. Some people also experience sensitivity to light and sound, irritability, a racing heart, or diarrhea. The severity varies widely from person to person and from one drinking episode to another, but the general experience is one of feeling physically drained and mentally foggy.
Researchers measure hangovers using standardized symptom scales, and among the most consistently reported symptoms, dizziness and overall fatigue rank near the top. These aren’t random discomforts. Each one traces back to a specific process happening inside your body as it recovers from alcohol exposure.
Why Your Body Feels This Way
When you drink, your liver breaks alcohol down in stages. The first step converts alcohol into acetaldehyde, a highly toxic substance that the National Institute on Alcohol Abuse and Alcoholism classifies as a known carcinogen. Acetaldehyde is short-lived because your body quickly converts it into a less harmful compound called acetate, but during its brief existence, it can damage cells in your liver, digestive tract, and potentially your brain. In animal studies, acetaldehyde alone produces sleepiness, poor coordination, and memory problems, effects that overlap heavily with hangover symptoms.
Alcohol also triggers your immune system. Studies have found that during a hangover, your body produces significantly higher levels of certain immune signaling molecules, the same types of molecules your body releases when you’re fighting off an infection. This immune overreaction helps explain why a hangover can feel so much like being sick, with nausea, headache, fatigue, and diarrhea all linked to this inflammatory response.
On top of all that, alcohol is a diuretic, meaning it makes you urinate more than the volume of liquid you’re taking in. The resulting dehydration contributes to thirst, dry mouth, and headache. Alcohol also irritates your stomach lining directly, which is why nausea and digestive discomfort are so common the next day.
Why Hangovers Wreck Your Sleep
One of the most underappreciated parts of a hangover is sleep disruption. Alcohol might help you fall asleep faster, but it dramatically reduces the quality of that sleep. On a normal night, your brain cycles through deep and light sleep stages six or seven times. After heavy drinking, that drops to just two or three cycles.
The reason is something called glutamine rebound. Glutamine is a natural stimulant your body produces, and alcohol suppresses its production while you’re drinking. Once alcohol clears your system, your body overcompensates by flooding itself with extra glutamine. This surge tends to hit during the second half of the night, causing frequent awakenings, lighter sleep, and less time in the restorative stages your brain needs. The result is that even if you slept for eight hours, you wake up feeling like you barely slept at all. This sleep disruption is a major reason hangovers impair concentration, reaction time, and even driving ability the following day.
When Symptoms Start and How Long They Last
Hangover symptoms don’t peak while you’re still drunk. They peak once your blood alcohol level drops back to roughly zero, which is why you often feel worst several hours after your last drink rather than immediately. For most people, this means symptoms are at their worst in the morning or early afternoon the day after drinking. Symptoms can persist for 24 hours or more, depending on how much you drank and individual factors like body weight, genetics, and hydration.
Why Some Drinks Cause Worse Hangovers
Not all alcoholic drinks produce equally bad hangovers. The difference comes down to congeners, chemical compounds that form naturally during fermentation and distillation. These include methanol, which your body breaks down into formaldehyde and formic acid, both highly toxic.
Dark spirits like bourbon, brandy, and whiskey contain the highest levels of congeners. Red wine is also relatively high. On the other end of the spectrum, vodka and beer contain the lowest levels. In one controlled study, participants who drank bourbon reported significantly worse hangover scores than those who drank the same amount of alcohol as vodka, even when both groups reached the same blood alcohol level of 0.11%. So while the total amount of alcohol matters most, your choice of drink plays a real role in how rough the next morning feels.
Do Hangover Remedies Actually Work
The market is flooded with hangover cure products. A survey of 82 commercially available hangover supplements found the most common ingredients were B vitamins, vitamin C, milk thistle extract, dihydromyricetin (DHM), and N-acetyl L-cysteine (NAC). Many of these are marketed with bold claims about preventing or curing hangovers.
The reality is less encouraging. A review of the scientific literature found no peer-reviewed human studies demonstrating that any of those 82 products actually work. Many products don’t even list the doses of their active ingredients, and the safe upper limits for several of these compounds haven’t been established. That doesn’t necessarily mean every ingredient is useless, but it does mean that no hangover pill has cleared the basic scientific bar of proving it does what it claims.
What does help, at least partially, is straightforward: drinking water between alcoholic drinks to reduce dehydration, eating before and during drinking to slow alcohol absorption, and pacing yourself to give your liver time to process each drink. Choosing lower-congener drinks like vodka or light beer over bourbon or red wine can also reduce symptom severity. None of these eliminate a hangover entirely, but they address the specific mechanisms that make hangovers worse.