Tiredness and thirst, almost universally. Then headache, nausea, trouble concentrating, and sensitivity to light and noise. Most people get some mix of those; almost nobody gets all of them; and about one in five drinkers claims to get none at all.
That is the honest shape of it, drawn from the validated scales researchers actually use. Below: what the symptoms are, what is known about why each one happens — including where the answer is "not much" — how long they last, and the short list of things that mean it is not a hangover at all.
What the research counts as a hangover symptom
Hangover research uses two validated inventories, and what they include is more informative than any listicle.
The Alcohol Hangover Severity Scale has twelve items: fatigue, clumsiness, dizziness, apathy, sweating, shivering, confusion, stomach pain, nausea, concentration problems, heart pounding, and thirst. Notice what is missing. It does not include headache — the symptom everyone assumes defines the condition turned out not to track overall severity well enough to earn a place.
The Hangover Symptoms Scale has thirteen: thirst, tiredness, headache, nausea, vomiting, weakness, concentration difficulty, sensitivity to light and sound, sweating, sleep trouble, anxiety, depression, and tremor.
Which ones people actually get. In a study of around 1,400 drinkers, fatigue was reported by 95.5% and thirst by 89.1% — the two near-universal ones. The cluster of fatigue, sleepiness and weakness explained more of overall severity than anything else, by a wide margin. In a larger sample, concentration problems and tiredness ranked highest; anxiety and low mood were reported least.
So the typical hangover, statistically, is a fatigue-and-thirst condition with cognitive fog, not the headache-and-vomiting one that cartoons draw.
Symptom by symptom — what is known, and what is not
Fatigue and sleepiness. The best-evidenced symptom and the most common. Alcohol gets you to sleep faster and then fragments the second half of the night — the NIAAA lists disrupted sleep as a core mechanism. You were unconscious for eight hours and slept for five. What alcohol does to sleep, in detail.
Thirst and dry mouth. Alcohol switches off the kidney's hold-water signal, so more leaves than usual. Real, well documented, and a smaller part of the overall picture than it feels like — the evidence on hydration and hangover is here.
Concentration problems and fog. Verster's review separates hangover into two clusters that occur together but independently: a hormonal, dehydration-linked cluster driving thirst, and an immune-signalling cluster driving the cognitive and mood symptoms. The fog is inflammation, not dryness, which is why water does not clear it.
Nausea and stomach pain. Alcohol irritates the stomach lining and increases acid production — the NIAAA's stated mechanism. What it is not, at the time you feel it, is acetaldehyde: that toxic intermediate has largely cleared by the time symptoms peak, which is a timing problem for the popular explanation. More on that here.
Headache. Here is where honesty costs us a tidy paragraph. Headache is common, it is in one validated scale and not the other, and the mechanism is not cleanly established. Mild fluid loss, blood vessel dilation and inflammatory signalling are all plausible contributors; no single one has been isolated as the driver. Anyone who tells you exactly why your head hurts is guessing with confidence.
Sensitivity to light and sound, and heart pounding. Both are validated symptom items. Neither has a well-isolated mechanism in the literature we could find. We are listing them as real and leaving the explanation blank rather than inventing one.
Sweating and shivering. Part of the general autonomic disturbance, listed in the scales, not separately explained. See also the tremor note below, because sweating alongside shaking has a second possible meaning.
Diarrhoea. Alcohol speeds gut transit so less water is reabsorbed, irritates the lining, and draws fluid into the bowel. The Cleveland Clinic explanation is a good one. Common, unglamorous, and it compounds the fluid loss.
Anxiety and low mood. Reported least often, and when they arrive they have their own name and their own article.
Tremor. Can be part of an ordinary hangover. It is also the first symptom of alcohol withdrawal in someone whose body has adapted to regular heavy drinking — and the difference matters enough to have its own section below.
Why some people say they never get one
Around 20–25% of drinkers describe themselves as hangover-resistant. That figure collapses with dose: at high blood alcohol levels only 8–15% still claim immunity, and among heavy drinkers only 5–6% report lifetime resistance. Most "I never get hangovers" is "I have not yet drunk enough."
The part that is genuinely interesting: people who clear alcohol faster report milder hangovers. Mackus and colleagues found residual ethanol the morning after correlated with nausea, concentration problems and sleepiness, and was significantly lower in the self-described resistant group. Some of what a hangover is turns out to be alcohol that has not left yet — which means part of hangover resistance is simply a faster liver. The elimination arithmetic.
How long the symptoms last
Measured once, directly: an average of a little over eighteen hours from the last drink, tracking sleep and severity rather than the number of drinks. The duration question has its own page.
What nobody has measured is which symptoms resolve first. The authors of that study flagged it as the obvious next question. So the intuition that thirst goes before fatigue, or that headache fades before fog, is exactly that — intuition — and we are not going to publish a sequence that does not exist.
When it is not a hangover
Three situations share symptoms with a hangover and are not one. Knowing the difference is the most useful thing on this page.
Alcohol poisoning is an overdose happening while alcohol is still on board. The NIAAA's signs: confusion or stupor, cannot be woken, vomiting while unconscious, seizures, fewer than eight breaths a minute or gaps of ten seconds or more, slow heart rate, clammy or bluish skin, low body temperature. Do not wait for all of them. Do not assume sleeping it off is safe. Call emergency services.
Alcohol withdrawal happens in people whose bodies have adapted to regular heavy drinking, and its timeline is the tell: tremor, sweating, anxiety and insomnia from 6–12 hours after the last drink; hallucinations possible within 24; seizure risk peaking at 24–48 hours; delirium tremens — the dangerous one — at 48–72. A hangover gets better across the day. Withdrawal gets worse. Worsening tremor, confusion out of proportion to the night, or anything hallucinatory is a doctor, not a breakfast.
Something else entirely. Symptoms that persist well into a second day, keep recurring after moderate drinking, or come with chest pain, severe abdominal pain, blood, or a stiff neck are not hangover territory. A hangover is a diagnosis of exclusion, and a supplement company is the wrong place to make it.
Frequently asked questions
What are the symptoms of a hangover? Most commonly fatigue and thirst, then concentration problems, headache, nausea, and sensitivity to light and sound. Validated research scales also include dizziness, sweating, stomach pain, heart pounding and tremor.
What is the most common hangover symptom? Fatigue, reported by over 95% of people in the largest symptom study, followed by thirst at nearly 90%. Headache is common but does not track overall severity well.
Why do I get hangovers so easily? Dose, sleep, how fast you personally clear alcohol, and what you drank all matter. Age does not make them worse — severity actually declines with age.
How long do hangover symptoms last? On average about eighteen hours from the last drink, tracking sleep and severity more than the amount consumed. No study has established which symptoms resolve first.
Why do some people not get hangovers? Partly dose — the figure collapses at high blood alcohol levels — and partly faster alcohol elimination, which shortens the time the body is exposed.
When should I see a doctor about a hangover? If symptoms are worsening rather than easing, if there is tremor that escalates, confusion, hallucinations or seizures, or if someone cannot be woken. Those are not hangover symptoms.
Where Snake Oil fits
Of everything on that list, the replaceable part is thirst and the fluid loss behind it — sodium, potassium and magnesium leaving with the water your kidneys were told not to keep. That is the symptom we built for: a stick in 16 ounces of water carrying 370mg of sodium, the 5g of carbohydrate that helps it absorb, and the potassium, magnesium, zinc, B lineup, vitamins C and E and glutamine-led amino acid blend alongside.†
The fatigue is the sleep you did not get, and the fog is your immune system finishing a job. Those are on their own clock. We would rather tell you which is which.
†These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Related reading: How long does a hangover last? · Hangxiety: why you feel anxious the day after drinking