Hangover Symptoms: What's Normal, Why It Happens, and What's Not a Hangover

Common hangover symptoms include fatigue, thirst, headache, nausea, poor concentration, sensitivity to light and sound, and anxiety, and they typically peak as blood alcohol returns to zero and ease within about a day.1,7 Confusion, vomiting that won't stop, seizures or slow breathing are not a hangover: they can signal alcohol poisoning and need emergency care.2

Key takeaways

  • In a survey of 1,410 Dutch students, fatigue (95.5%) and thirst (89.1%) were the most commonly reported symptoms, but drowsiness and thinking problems drove severity.3
  • Symptoms peak when blood alcohol returns to about zero and can last 24 hours or longer.1
  • Dehydration markers and blood sugar don't track how bad a hangover feels; immune markers show the most convincing link.4
  • Shakiness, sweating and a racing heart starting within about 8 hours of the last drink, after heavy drinking, can be alcohol withdrawal, which can turn dangerous.5
  • Fewer than 8 breaths a minute, seizures, confusion or being impossible to wake are signs of alcohol poisoning: call 911.2

What counts as a hangover?

Researchers define a hangover as the negative mental and physical symptoms that can follow a single episode of drinking, starting as blood alcohol approaches zero. The 2020 definition dropped "heavy drinking" because hangovers can follow modest amounts.6 Being confused or impossible to wake while alcohol is still in your blood is something else, and more dangerous.2

What are the most common hangover symptoms?

Fatigue and thirst top the list, followed by drowsiness, headache, dry mouth and nausea. NIAAA's list of typical symptoms also includes weakness, muscle aches, stomach pain, vertigo, sensitivity to light and sound, anxiety, irritability, sweating and increased blood pressure.1

But "drowsiness" (sleepiness, fatigue, weakness) and "cognitive problems" (poor alertness, memory and concentration) drive overall misery most; thirst and dry mouth contribute much less.3

Average hangover symptom severity (0 = absent, 10 = extreme) in 396 Dutch students whose hangover eased steadily through the day, the most common pattern
Symptom Average severity (0–10)
Fatigue 6.6
Thirst 6.0
Drowsiness 5.9
Headache 5.4
Dry mouth 5.3
Nausea 5.0
Weakness 4.6
Concentration problems 4.1
Dizziness 2.3
Tremor 2.0
Shivering 1.5
Heart pounding 0.8
Anxiety 0.2

Data: a 2018 reanalysis of 727 students' reports.7 Anxiety scored low here, yet a 2026 review of 22 studies linked hangovers with more anxiety, stress and low mood; see hangxiety.8

Why does each symptom happen?

Most trace back to disrupted sleep, an immune response, stomach irritation, fluid loss and the brain readjusting as alcohol wears off. Dehydration matters less than most people think.

Leading explanations for common hangover symptoms, and how strong the evidence is
Symptom Leading explanation Evidence
Fatigue, drowsiness, brain fog Alcohol fragments the second half of the night and reduces REM sleep9 Strong
Thirst, dry mouth Alcohol suppresses vasopressin, the hormone that tells the kidneys to hold water1 Strong for thirst; weak for overall severity
Nausea, stomach pain Alcohol irritates the stomach lining and increases acid1 Established
Aches, feeling ill, headache Immune signals such as IL-6 and CRP rise with hangover severity10 Moderate, mostly correlational
Anxiety, irritability The brain rebounding as alcohol's calming effect wears off1 Plausible

A 2024 review called hangover and dehydration "two co-occurring but independent consequences" of drinking.11 The full story is in what causes a hangover.

Are chills, fever, diarrhea and a racing heart hangover symptoms?

Chills, diarrhea, dizziness and a fast heartbeat can be. A fever or an irregular heartbeat points elsewhere.

Chills and sweats. Shivering averaged 1.5 out of 10 in the student data.7 It hasn't been studied directly. One hypothesis is that hangovers are an inflammation-driven "sickness behavior," the achy, shivery state you get with an infection.12

Fever. Fever isn't on NIAAA's symptom list.1 It suggests an infection, food poisoning or, in someone who has been drinking heavily and then stops, delirium tremens, a severe form of withdrawal that needs emergency care.13,5

Diarrhea. Alcohol reduces the contractions that hold food in the small intestine for digestion, shortening transit time, and acetaldehyde can build up in the colon. Much of that research involves heavy drinkers.14

Dizziness. Vertigo is on NIAAA's list. Stand up slowly, and don't drive: hangovers impair attention and coordination even at zero blood alcohol.1

A racing heart. Alcohol pushes heart rate up: among 4,098 Finnish employees wearing monitors, heart rate stayed higher during the first 3 hours of sleep on drinking nights.15 A heartbeat that feels irregular, not just fast, is different: after heavy drinking it's a withdrawal sign that warrants emergency care.5

Is it a hangover or something else?

A hangover should be steadily easing, not getting worse, and shouldn't involve confusion, fever or being unable to keep water down.

Hangover look-alikes: timing, telltale signs and what to do
Condition Typical timing Signs that point to it What to do
Alcohol poisoning During or soon after drinking; blood alcohol can keep rising after the last drink Confusion, can't be woken, vomiting, seizures, fewer than 8 breaths a minute, bluish or clammy skin Call 9112
Alcohol withdrawal Usually within 8 hours of the last drink, peaking at 24–72 hours, after heavy drinking Shakiness, anxiety, sweating, rapid heart rate, insomnia; fever, hallucinations or seizures when severe See a doctor promptly; 911 for seizures, fever, severe confusion or hallucinations5
Concussion After any fall, bump or blow to the head A headache that gets worse and doesn't go away, repeated vomiting, one pupil larger than the other, slurred speech 911 or the emergency department16
Food poisoning Often 2–6 hours after eating Cramps, diarrhea, vomiting, fever and chills See a provider for bloody stools, a fever above 101°F or if you can't keep fluids down13

More detail: signs of alcohol poisoning and hangover or something else?

What does a typical hangover timeline look like?

In a 1974 study of 23 men, average severity peaked 12 to 14 hours after drinking stopped and was gone by 16 to 21 hours. Among 727 students, 54.5% had a hangover that eased steadily from waking, 21.8% one that peaked later, with more stomach complaints, and 19.1% a milder, flat one.7 See how long a hangover lasts.

What helps each symptom?

Only time reliably ends a hangover; a 2022 review of 21 placebo-controlled trials found only very low-quality evidence for any remedy.1,17 You can still make the day easier:

  • Fatigue and fog: rest, and protect the next night's sleep.
  • Thirst: drink water. It helps thirst, though it didn't change overall severity in studies.11
  • Nausea: small sips and bland food; see hangover nausea.
  • Headache: see hangover headache and the caution below.
  • More alcohol: skip it. "Hair of the dog" can prolong the malaise.1

Our how to cure a hangover guide has a full morning plan. The surest prevention is drinking less: US guidance says to "consume less alcohol for better overall health"; pregnant women, people in recovery or unable to control their drinking, and people on interacting medicines shouldn't drink at all.18

What we don't know yet

Most symptom data come from young Dutch students, so the averages may not fit older adults.7 Next-day chills, diarrhea and heart symptoms have barely been studied on their own, and nobody can fully explain why, after the same amount, some people get severe hangovers and others almost none.4

Frequently asked questions

Can a hangover cause a fever?

Not typically. Fever isn't on NIAAA's list of hangover symptoms, though sweating is.1 A measured fever points to an infection, food poisoning or, after a period of heavy drinking, severe alcohol withdrawal, which needs emergency care.5

Why do I get chills when I'm hungover?

Hangover chills haven't been studied directly. One hypothesis is that the inflammatory response to drinking produces a mild version of the shivery, achy feeling of being sick.12 Chills with a fever deserve a closer look.

Why does my heart race when I'm hungover?

Alcohol raises heart rate, and the effect carries into sleep: in 4,098 Finnish employees, heart rate stayed elevated for the first 3 hours of sleep after drinking.15 Too much caffeine can add to it.21 A racing heart with tremor and sweating after heavy drinking can be withdrawal; an irregular heartbeat then warrants emergency care.5

Can a hangover cause diarrhea?

It can. Alcohol shortens the time food spends in the intestines, and acetaldehyde can build up in the colon, though much of that research involves heavy drinkers.14 Bloody diarrhea, a fever above 101°F or diarrhea that hasn't improved in 5 days is more likely an infection or food poisoning and worth seeing a provider about.13

Is shaking after drinking a hangover or withdrawal?

Mild tremor shows up in hangover surveys, usually at low intensity.7 Shakiness that starts within about 8 hours of your last drink after heavy or daily drinking, with anxiety, sweating and a racing heart, may be alcohol withdrawal, which can turn dangerous quickly.5 Don't treat it with more alcohol; talk to a doctor.

Sources

  1. National Institute on Alcohol Abuse and Alcoholism (NIAAA). Hangovers. Updated December 2025. NIAAA
  2. NIAAA. Understanding the Dangers of Alcohol Overdose. Updated December 2025. NIAAA
  3. Penning R, et al. Alcohol hangover symptoms and their contribution to the overall hangover severity. Alcohol Alcohol. 2012;47(3):248-252. PubMed
  4. Penning R, et al. The pathology of alcohol hangover. Curr Drug Abuse Rev. 2010;3(2):68-75. PubMed
  5. MedlinePlus (NIH). Alcohol withdrawal. Reviewed January 1, 2025. MedlinePlus
  6. Verster JC, et al. Updating the definition of the alcohol hangover. J Clin Med. 2020;9(3):823. PubMed
  7. Verster JC, et al. Differences in the temporal typology of alcohol hangover. Alcohol Clin Exp Res. 2018;42(4):691-697. PubMed
  8. Rothman R, et al. A systematic review of the impact of the alcohol hangover upon negative affect. Drug Alcohol Rev. 2026;45(1):e70052. PubMed
  9. Ebrahim IO, et al. Alcohol and sleep I: effects on normal sleep. Alcohol Clin Exp Res. 2013;37(4):539-549. PubMed
  10. van de Loo AJAE, et al. The inflammatory response to alcohol consumption and its role in the pathology of alcohol hangover. J Clin Med. 2020;9(7):2081. PubMed
  11. Mackus M, et al. Alcohol hangover versus dehydration revisited: the effect of drinking water to prevent or alleviate the alcohol hangover. Alcohol. 2024;121:9-18. PubMed
  12. Turner BRH, et al. Inflammation, oxidative stress and gut microbiome perturbation: a narrative review of mechanisms and treatment of the alcohol hangover. Alcohol Clin Exp Res (Hoboken). 2024;48(8):1451-1465. PubMed
  13. MedlinePlus (NIH). Food poisoning. Reviewed October 20, 2025. MedlinePlus
  14. Bode C, Bode JC. Alcohol's role in gastrointestinal tract disorders. Alcohol Health Res World. 1997;21(1):76-83. PubMed
  15. Pietilä J, et al. Acute effect of alcohol intake on cardiovascular autonomic regulation during the first hours of sleep in a large real-world sample of Finnish employees: observational study. JMIR Ment Health. 2018;5(1):e23. PubMed
  16. CDC. HEADS UP: Signs and Symptoms of Concussion. September 2025. CDC
  17. Roberts E, et al. The efficacy and tolerability of pharmacologically active interventions for alcohol-induced hangover symptomatology: a systematic review of the evidence from randomised placebo-controlled trials. Addiction. 2022;117(8):2157-2167. PubMed
  18. USDA and HHS. Dietary Guidelines for Americans, 2025–2030. January 2026. PDF
  19. FDA. 21 CFR 201.326: required warnings for over-the-counter pain relievers. eCFR
  20. SAMHSA. National Helpline. SAMHSA
  21. FDA. Spilling the Beans: How Much Caffeine Is Too Much? August 2024. FDA

Published by Fuller Health, which makes After Party. This article is general information, not medical advice: talk to a doctor or pharmacist about your own health, medicines and drinking. Last reviewed October 9, 2026. How we research and write.

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