A hangover is a combination of negative physical and mental symptoms that show up after drinking alcohol, typically kicking in as your body finishes processing the alcohol out of your system. You don’t need to have been blackout drunk to have one. Researchers have confirmed that hangovers can follow even moderate drinking sessions, not just heavy ones. If you drank last night and woke up feeling like a worse version of yourself, here’s how to tell what’s going on.
The Core Physical Symptoms
Hangovers hit the body in a recognizable pattern. The most common physical symptoms are fatigue, headache, thirst, nausea, stomach pain, and dizziness. These tend to be the first things you notice. Clinical tools used to measure hangover severity track exactly these symptoms on a scale from “none” to “incapacitating,” and most people land somewhere in between.
Beyond the obvious ones, your body may also show signs of its nervous system working overtime: a noticeably faster heartbeat, mild tremor in your hands, and sweating even when you’re not hot. Increased sensitivity to light and sound is common too, which is why a bright room or a loud TV can feel genuinely painful. Red, bloodshot eyes and general muscle aches round out the picture. If you’re checking off several items on this list, you’re almost certainly hungover.
The Mental and Emotional Side
A hangover isn’t just physical. Many people experience a foggy, slowed-down feeling in their thinking, along with irritability, low mood, or a vague sense of dread. If you feel unusually anxious the morning after drinking, that’s so common it has its own name: “hangxiety.”
There’s a straightforward chemical explanation. Alcohol boosts your brain’s calming signals and suppresses its alertness signals while you’re drinking. That’s the relaxed, uninhibited feeling. But as the alcohol leaves your system, your brain overcorrects. It dials down the calming signals and cranks up the alertness signals, which creates a rebound effect that feels like anxiety, restlessness, or even mild panic. The important thing to recognize is that this anxiety is chemical, not necessarily a reflection of something you did or said the night before.
How a Hangover Affects Your Brain
If you feel slower, clumsier, or just “off,” that’s not your imagination. Studies show that hangovers measurably impair working memory, executive function, and reaction time. The more severe the hangover, the worse the impairment. Reaction time slows more reliably than accuracy drops, which means you might still get things right but take noticeably longer to do them.
To put this in practical terms: research has found that hangover-related driving impairment is comparable to having a blood alcohol concentration of 0.05 to 0.08%, which is at or near the legal limit in most places. You may feel sober and still be performing as if you aren’t. This matters if you’re planning to drive, operate equipment, or do anything requiring sharp focus.
When Symptoms Start and How Long They Last
Hangover symptoms typically begin as your blood alcohol concentration drops toward zero, which is why you often feel fine going to bed but terrible waking up. The timeline depends on how much you drank and how quickly your body metabolizes alcohol. For most people, symptoms peak in the morning hours and gradually improve throughout the day.
How fast your body breaks down alcohol plays a direct role in severity. People who metabolize alcohol more quickly tend to have less severe hangovers, likely because the alcohol spends less time reaching the brain. This helps explain why hangovers can feel different from person to person, or even from one occasion to the next. Factors like how much you ate, how hydrated you were, how well you slept, and your overall health all shift the equation.
What’s Actually Causing It
The popular explanation is dehydration, and while alcohol does make you urinate more and lose fluids, dehydration alone doesn’t account for most hangover symptoms. The full picture involves several processes happening at once.
Your liver breaks down alcohol in two steps. First, it converts alcohol into a toxic byproduct. Then it converts that byproduct into something harmless. The speed of both steps matters. While that toxic intermediate compound builds up, your body also mounts an inflammatory and oxidative stress response. Studies have found that markers of oxidative stress correlate significantly with hangover severity. In short, a hangover is your body dealing with a mild toxic event, not just being thirsty.
Congeners, the chemical byproducts of fermentation that give darker drinks their color and flavor, can also intensify symptoms. Drinks like bourbon, red wine, and brandy tend to contain more of these compounds than vodka or gin, which is one reason the same amount of alcohol can produce different hangovers depending on what you drank.
Hangover vs. Something More Serious
A standard hangover is miserable but not dangerous. It gets better on its own within roughly 24 hours. Alcohol poisoning, on the other hand, is a medical emergency and looks distinctly different.
The red flags that separate alcohol poisoning from a hangover include:
- Inability to wake up or difficulty staying conscious
- Seizures
- Slow breathing: fewer than 8 breaths per minute, or gaps of 10 seconds or more between breaths
- Extremely low body temperature, bluish skin, or paleness
- No gag reflex, which creates a serious choking risk if the person vomits
- Mental confusion beyond normal grogginess
These symptoms usually appear while someone is still intoxicated or shortly after they stop drinking, not the next morning. If you see these signs in someone else, or you’re experiencing them yourself, that’s not a hangover. Alcohol overdose happens when alcohol suppresses the brain areas that control breathing, heart rate, and temperature, and it can be fatal without treatment.
A Simple Self-Check
If you’re wondering whether what you’re feeling is a hangover, run through this quick checklist. You drank alcohol in the past 12 to 24 hours. You’re experiencing some combination of headache, nausea, fatigue, thirst, dizziness, stomach discomfort, or racing heart. You may also feel anxious, foggy, or irritable. Your symptoms started as the effects of alcohol wore off, not while you were still drinking. And you’re generally improving, even if slowly.
If all of that matches, you’re hungover. The only real cure is time, fluids, food, and rest. Your body is already doing the work of clearing everything out. The symptoms are the cleanup process.