Hangover: What Causes It, and Why Time Is the Only Sure Cure
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer
A hangover is a group of unpleasant symptoms, including tiredness, thirst, headache, nausea and mood changes, that typically strike the morning after drinking too much alcohol [1]. Most pass on their own within 24 hours, and time is the only sure cure [1] [2]. Fluids, bland foods and sleep help [2]. The only guaranteed prevention is not drinking alcohol [1].
What the research says
No hangover remedy has solid evidence behind it. A systematic review of 21 placebo-controlled randomized trials (386 participants) found that no two studies tested the same intervention, so no meta-analysis was possible, and all efficacy evidence was rated very low quality; a few single trials, for example of clove extract, tolfenamic acid and pyritinol, reported lower hangover symptom scores than placebo and were judged worth further study (Roberts et al., Addiction, 2022) [3].
Hangovers likely involve several biological factors, not just dehydration. A narrative review of animal and human hangover research concluded that alcohol metabolites, neurotransmitter changes, inflammatory factors and mitochondrial dysfunction are the most likely contributors, and noted that many human studies are not well controlled (Palmer et al., Alcohol Alcohol, 2019) [4].
What Is a Hangover?
A hangover is a group of unpleasant symptoms that can happen after drinking too much alcohol [1]. The consequences extend beyond the physical discomfort: frequent hangovers are linked with poor performance and conflict at home, at school, and at work [1].
As a general rule, the more alcohol you drink, the more likely you are to have a hangover the next day. However, there is no easy way to know exactly how much you can drink and still avoid one [1]. Some people get a hangover from a single drink, while others can drink heavily and escape it [1]. The encouraging news is that most hangovers go away on their own, though they can last up to 24 hours [1].
Hangover Symptoms
Hangover symptoms often begin when your blood alcohol content drops and is at or near zero [1]. They are usually in full effect the morning after a night of heavy drinking [1]. Depending on what and how much alcohol you drank, you may notice any of the following [1]:
Extreme tiredness and weakness.
Thirst and dry mouth.
Headache and muscle aches.
Nausea, vomiting, or belly pain.
Poor sleep, or not getting enough sleep.
Low tolerance for light and sound.
Dizziness or a sense of the room spinning.
Shakiness and sweating.
Trouble concentrating or thinking clearly.
Mood changes, such as depression, anxiety, and irritability.
Fast heartbeat.
Figure 1: Common hangover symptoms include thirst and dry mouth, headache, trouble concentrating, nausea, extreme tiredness, and low tolerance for light and sound.
Why Hangovers Happen: Five Ways Alcohol Punishes Your Body
Alcohol itself causes a hangover, but several issues contribute to the misery [1]. Understanding them explains why hangover symptoms feel the way they do.
Alcohol makes you urinate more. You lose extra body fluid, which can lead to dehydration. Dehydration produces extra thirst, tiredness, headache, dizziness, and lightheadedness [1].
Alcohol triggers an immune system response. The inflammatory response commonly causes physical symptoms that make you feel as if you're ill. It can also cause trouble thinking clearly and remembering, poor appetite, and loss of interest in usual activities [1].
Alcohol irritates the stomach. It irritates the lining of the stomach and causes the stomach to make more acid, which can lead to belly pain, nausea, or vomiting [1].
Alcohol can lower blood sugar. If blood sugar dips too low, you may feel extra tired, weak, and shaky. Low blood sugar can also cause mood changes and even seizures [1].
Alcohol prevents restful sleep. You may feel sleepy, but alcohol keeps you from getting the kind of sleep that helps you feel rested. It often causes you to wake in the middle of the night or too early in the morning [1], leaving you groggy and tired.
Figure 2: Five ways alcohol contributes to hangover symptoms: dehydration, an inflammatory immune response, stomach irritation, low blood sugar, and poor sleep.
The Role of Congeners
Alcoholic beverages contain ingredients called congeners, which give many drinks their taste and smell. Congeners can play a role in hangovers, and they appear in larger amounts in dark liquors such as brandy and bourbon than in clear liquors such as vodka and gin [1]. Drinks with more congeners are more likely to produce a hangover or make one worse. But drinking too much alcohol of any color can still leave you feeling bad the next morning [1].
Risk Factors: Who Gets Hangovers More Often?
Anyone who drinks alcohol can have a hangover. Some people are simply more prone to them than others. A difference in a gene that affects how the body breaks down alcohol may make some people flush, sweat, or become ill after even a small amount [1].
Drinking on an empty stomach: having no food in your stomach speeds up how much and how fast alcohol enters the body [1].
Using nicotine or other drugs with alcohol: smoking along with drinking appears to raise the likelihood of a hangover [1].
Not sleeping well or long enough after drinking: some researchers believe certain hangover symptoms are due, at least in part, to lost sleep [1].
Family history of alcohol use disorder: this may suggest an inherited problem with the way your body processes alcohol [1].
Drinking darker colored beverages: darker drinks often contain a high level of congeners [1].
The Wine Headache
Some people develop a headache a few hours after drinking wine, especially red wine. The cause isn't clear, and it's different from a hangover, which may or may not include a headache. It's possible that some chemicals in wine and the way the body responds to them could result in the headache. More research is needed to find the exact cause [1].
Hangover Complications: The Day-After Costs
A hangover is more than an uncomfortable morning. When you have a hangover, you're likely to have problems with clear thinking and memory, attention and focus, and tasks that require steady hands and body coordination [1]. This short-term dulling of your abilities increases your risk of real-world problems:
When to See a Doctor
Hangovers after a single night of drinking go away on their own, so people usually don't visit a healthcare professional for a hangover diagnosis [2]. Your symptoms the morning after drinking, such as tiredness, dry mouth, headache, nausea, trouble thinking clearly, and low tolerance for light and sound, are usually all the evidence anyone needs [2].
However, talk with your healthcare professional if you're concerned that frequent heavy drinking may lead to serious problems, such as alcohol withdrawal [1]. Regular hangovers that affect your quality of life, including personal relationships or your performance at school or work, are worth discussing, because treatment for problems with alcohol is widely available [2].
Alcohol Poisoning: When It's an Emergency
More-serious symptoms from heavy drinking may be a sign of alcohol poisoning, a life-threatening emergency. It results from drinking large amounts of alcohol in a short period and can affect breathing, heart rate, body temperature, and the gag reflex. In some cases, it can lead to coma and death [1]. Call 911 or your local emergency number immediately if a person who has been drinking shows any of these signs [1]:
Confusion.
Vomiting.
Seizures.
Slow breathing: fewer than eight breaths a minute [1].
Irregular breathing: a gap of more than 10 seconds between breaths [1].
Damp or sweaty skin.
Blue or gray skin color from low oxygen levels (may be harder to see depending on skin color).
Slow heart rate.
Low body temperature.
Difficulty remaining conscious.
Passing out and not being able to be awakened.
A person who can't be awakened is at risk of dying. If you suspect alcohol poisoning, even if you don't see the classic symptoms, get medical help right away [1].
Treatment: What Actually Works for a Hangover
Time is the only sure cure for a hangover [2]. Symptoms can last up to 24 hours [2]. In the meantime, four practical steps can help you feel better:
Fill your water bottle. Sip water or fruit juice to prevent dehydration. Resist any temptation to treat your hangover with more alcohol, because it will only make you feel worse [2].
Have a snack. Bland foods, such as toast and crackers, may boost your blood sugar and settle your stomach. Bouillon soup can help replace lost salt and potassium [2].
Take a pain reliever. A standard dose of an over-the-counter pain reliever may ease a headache. But be careful: aspirin and ibuprofen can irritate your stomach, and the combination of alcohol and acetaminophen can cause serious liver damage [2].
Go back to bed. If you sleep long enough, your hangover may be gone when you wake up [2].
Figure 3: Four supportive steps that ease a hangover while time does the healing.
A Note on Preventive Pain Relievers
Some people take pain relievers to prevent hangover symptoms before they start. Ask your healthcare professional first whether this is safe for you and how much is best, because these medicines may not work well together with other medicines you take [1]. Aspirin and ibuprofen can cause the stomach to make more acid and irritate it, and acetaminophen may cause serious liver damage if taken with too much alcohol [1].
Alternative Remedies: What the Evidence Says
Many alternative remedies are marketed for hangovers. Studies, however, haven't found any natural remedies that consistently or effectively improve hangover symptoms [2]. Keep in mind that natural doesn't always mean safe. Talk with your healthcare professional before trying any alternative medicine so you understand the possible risks and benefits [2].
Prevention: How to Reduce Your Odds
Some companies use misleading advertising to claim their products can prevent hangovers [1]. The only guaranteed way to prevent a hangover is to not drink alcohol [1]. If you choose to drink, do so in moderation. For healthy adults, moderate use means up to one drink a day for women and up to two drinks a day for men [1]. The less alcohol you drink, the less likely you are to have a hangover.
Eat before and while drinking. Alcohol enters the body more quickly if your stomach is empty [1].
Choose carefully. Beverages with fewer congeners are slightly less likely to cause hangovers, though all types of alcohol can [1].
Drink water between alcoholic drinks. A full glass of water after each drink helps you stay hydrated and helps you drink less alcohol [1].
Know your limits. Decide ahead of time how many drinks you'll have [1], stick to it, and don't feel pressured to drink.
Take it slow. Don't have more than one alcoholic drink in an hour [1], and stop when you've reached your limit, or before.
Conclusion: Respect the Morning After
A hangover is your body's bill for alcohol that arrived faster than it could be processed, through dehydration, inflammation, stomach irritation, low blood sugar, and lost sleep. There is no shortcut around it: time is the only sure cure, supported by fluids, bland food, careful pain relief, and rest.
The smartest strategy is prevention. Eating before drinking, having water with your drinks, pacing yourself, and staying within moderate limits reduce your odds of a hangover. And if hangovers keep becoming a pattern, that is a signal worth listening to: treatment for alcohol-related problems is widely available, and starting the conversation with your healthcare professional is a step toward lasting change. If you or someone you know is drinking more than intended, talk with a healthcare professional. Help is available.
Frequently Asked Questions
What is a hangover?
A hangover is a group of unpleasant symptoms that can happen after drinking too much alcohol, including tiredness, thirst, headache, nausea, trouble concentrating, and mood changes. Symptoms usually begin when blood alcohol levels drop to or near zero, are in full effect the morning after heavy drinking, and typically go away on their own within 24 hours.
What causes a hangover?
Several issues contribute: alcohol makes you urinate more and become dehydrated, triggers an inflammatory immune response, irritates the stomach lining and raises stomach acid, can lower blood sugar, and prevents restful sleep. Darker liquors with more congeners, like brandy and bourbon, are more likely to produce a hangover than clear liquors.
Can you cure a hangover?
Time is the only sure cure, and symptoms can last up to 24 hours. In the meantime, sipping water or fruit juice, eating bland foods like toast and crackers, taking a standard-dose pain reliever carefully, and going back to sleep can help you feel better. Studies haven't found any natural remedies that consistently or effectively improve hangover symptoms.
Why does drinking more alcohol ("hair of the dog") make a hangover worse?
Mayo Clinic advises resisting any temptation to treat a hangover with more alcohol because it will only make you feel worse. Hangover symptoms begin when your blood alcohol level drops near zero, and more alcohol adds to the dehydration, stomach irritation, and poor sleep that contribute to them.
What should you eat and drink for a hangover?
Sip water or fruit juice to prevent dehydration, and have bland foods such as toast and crackers, which may boost your blood sugar and settle your stomach. Bouillon soup can help replace lost salt and potassium.
Are hangovers contagious?
No. A hangover results from your own alcohol intake. But the day-after effects can spill over to the people around you through poor performance, missed obligations, and conflict at home, school, and work.
How long does a hangover last?
Most hangovers go away on their own, though they can last up to 24 hours. Symptoms often begin when your blood alcohol content drops to or near zero and are usually in full effect the morning after a night of heavy drinking.
Are dark liquors worse for hangovers than clear ones?
Dark liquors such as brandy and bourbon contain more congeners than clear liquors such as vodka and gin. Congeners are more likely to produce a hangover or make one worse, but drinking too much alcohol of any color can still make you feel bad the next morning.
Can hangovers be dangerous?
A hangover itself usually goes away on its own, but heavy drinking can also cause alcohol poisoning, a life-threatening emergency. Warning signs include confusion, vomiting, seizures, slow or irregular breathing, blue or gray skin, and passing out. Call 911 or your local emergency number right away.
When should you see a doctor about hangovers?
Talk with a healthcare professional if you're concerned that frequent heavy drinking may lead to serious problems such as alcohol withdrawal, or if regular hangovers affect your relationships or your performance at school or work. Treatment for problems with alcohol is widely available.
Related Reading
Blood Alcohol Content (BAC): What It Measures, BAC Levels and Effects, and What Results Mean explains BAC levels, how fast your liver clears alcohol and what each level does to your body.
Medical Disclaimer
The information in this article is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have about a medical condition.
References
Mayo Clinic Staff. Hangovers - Symptoms and causes. Mayo Clinic. January 30, 2024. https://www.mayoclinic.org/diseases-conditions/hangovers/symptoms-causes/syc-20373012
Mayo Clinic Staff. Hangovers - Diagnosis and treatment. Mayo Clinic. January 30, 2024. https://www.mayoclinic.org/diseases-conditions/hangovers/diagnosis-treatment/drc-20373015
Roberts E, Smith R, Hotopf M, 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. PMID 34972259. https://doi.org/10.1111/add.15786
Palmer E, Tyacke R, Sastre M, et al. Alcohol hangover: underlying biochemical, inflammatory and neurochemical mechanisms. Alcohol Alcohol. 2019;54(3):196-203. PMID 30916313. https://doi.org/10.1093/alcalc/agz016
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