Hangover symptoms often begin when your blood alcohol content drops and is at or near zero. Symptoms are usually in full effect the morning after a night of heavy drinking. Depending on what and how much alcohol you drank, you may notice:

• 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.
• Problems concentrating or thinking clearly.
• Changes in mood, such as depression, anxiety and irritability.
• Fast heartbeat.

When to see a doctor

Hangovers after a single night's drinking go away on their own. Talk with your healthcare professional if you're concerned that frequent heavy drinking may lead to serious problems, such as alcohol withdrawal.

When it's an emergency

More-serious symptoms from heavy drinking may be a sign of alcohol poisoning — a life-threatening emergency. Alcohol poisoning is a serious and sometimes deadly result of drinking large amounts of alcohol in a short period of time. Drinking too much too quickly can affect breathing, heart rate, body temperature and gag reflex. In some cases, this can lead to coma and death.

Call 911 or your local emergency number if a person who has been drinking shows symptoms of:

• Confusion.
• Vomiting.
• Seizures.
• Slow breathing — less than eight breaths a minute.
• Irregular breathing — a gap of more than 10 seconds between breaths.
• Damp or sweaty skin.
• Blue or gray skin color due to low oxygen levels. Depending on skin color, these changes may be harder to see.
• 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 that someone has alcohol poisoning — even if you don't see the classic symptoms — get medical help right away.

Hangovers are caused by drinking too much alcohol. A single alcoholic drink is enough to trigger a hangover for some people, while others may drink heavily and not have a hangover.

Several issues may contribute to a hangover. For example:

• Alcohol causes the body to make more urine. You lose extra body liquid by urinating more than usual. This can lead to dehydration. Symptoms of dehydration include extra thirst, tiredness, headache, dizziness and lightheadedness.
• Alcohol triggers an inflammatory response from the immune system. The immune system may make certain substances linked to the body's defense system. This commonly causes physical symptoms that make you feel as if you're ill. Your symptoms also may include problems thinking clearly and remembering, poor appetite, and loss of interest in usual activities.
• Alcohol irritates the lining of the stomach. Alcohol can irritate your stomach. Alcohol also causes your stomach to make more acid. This can cause belly pain, nausea or vomiting.
• Alcohol can cause blood sugar levels to fall. If your blood sugar dips too low, you may feel extra tired, weak and shaky. You also may have mood changes and even seizures.
• Alcohol prevents restful sleep. You may feel sleepy, but alcohol keeps you from getting the kind of sleep that helps you feel rested. Alcohol also often causes you to awaken in the middle of the night or too early in the morning. Not getting good-quality sleep may leave you groggy and tired.

Congeners

Alcoholic beverages contain ingredients called congeners. These give many types of alcoholic beverages their taste and smell. They also can play a role in hangovers. Congeners are found in larger amounts in dark liquors, such as brandy and bourbon, than in clear liquors, such as vodka and gin.

Congeners are more likely to produce a hangover or make a hangover worse. But drinking too much alcohol of any color can still make you feel bad the next morning.

Anyone who drinks alcohol can have a hangover. But some people are more likely to have hangovers than others are. A difference in a gene that affects the way the body breaks down alcohol may make some people flush, sweat or become ill after drinking even a small amount of alcohol.

Issues that may make a hangover more likely or worse include:

• Drinking on an empty stomach. Having no food in your stomach speeds up how much and how fast alcohol enters the body.
• Using other drugs, such as nicotine, along with alcohol. Smoking along with drinking appears to raise the likelihood of a hangover.
• Not sleeping well or long enough after drinking. Some researchers believe that certain hangover symptoms are often due, at least in part, to how much sleep you get following a night of drinking. Poor-quality sleep and not getting enough sleep usually follow drinking alcohol.
• Having a family history of alcohol use disorder. Having close relatives with a history of alcohol use disorder may suggest an inherited problem with the way your body processes alcohol.
• Drinking darker colored alcoholic beverages. Darker colored drinks often contain a high level of congeners and may be more likely to produce a hangover.

Wine headache

Some people have a headache a few hours after drinking wine — especially red wine. The cause of the headache isn't clear. But it's different from a hangover, which may or may not include a headache. It's possible that some chemicals in wine and how the body responds to them could result in a headache after drinking wine. More research is needed to find the exact cause of wine headache.

When you have a hangover, you're likely to have problems with:

• Clear thinking and memory.
• Attention and focus.
• Tasks that require steady hands and body coordination.

Not surprisingly, this short-term dulling of your abilities increases your risk of problems at home, school and work, such as:

• Problems being on time or not showing up at all.
• Trouble finishing tasks.
• Conflict with others.
• Falling asleep at school or on the job.
• Problems driving a car or using machinery.
• Workplace injuries.

Some companies use misleading advertising to claim that their products can prevent hangovers. But the only guaranteed way to prevent a hangover is to not drink alcohol.

If you choose to drink alcohol, do so in moderation. Moderate alcohol use for healthy adults means:

• Up to one drink a day for women.
• Up to two drinks a day for men.

The less alcohol you drink, the less likely you are to have a hangover. It may help to:

• Eat before and while drinking. Alcohol enters the body more quickly if your stomach is empty. It may help to eat something before drinking alcohol and during the time you're drinking.
• Choose carefully. Beverages with fewer congeners are slightly less likely to cause hangovers than beverages with more congeners. But remember that all types of alcohol can cause a hangover.
• Drink water between alcoholic drinks. Drinking a full glass of water after each alcoholic drink will help you stay hydrated. It'll also help you drink less alcohol.
• Know your limits and only drink in moderation. Decide ahead of time how many drinks you'll have — and stick to it. Don't feel pressured to drink.
• Take it slow. Don't have more than one alcoholic drink in an hour. Stop drinking completely when you've reached your limit — or before then.

Some people take pain relievers to prevent hangover symptoms. But ask your healthcare professional if this is safe for you and how much medicine is best for you. These medicines may not work well together with other medicines you take.

Aspirin and ibuprofen (Advil, Motrin IB, others) can cause your stomach to make more acid, which can irritate your stomach. And acetaminophen (Tylenol, others) may cause serious liver damage if taken with too much alcohol.

People usually don't go to a healthcare professional to get a diagnosis or treatment for a hangover. Mostly likely, you'll know if you have a hangover based on your symptoms the morning after drinking alcohol. Common symptoms include tiredness, dry mouth, headache, nausea, problems thinking clearly, and low tolerance for light and sound.

Talk to your healthcare professional if regular hangovers affect your quality of life, including your personal relationships or your performance at school or work. Treatment for problems with alcohol is widely available.

Time is the only sure cure for a hangover. Symptoms can last up to 24 hours. In the meantime, here are a few things you can do to help yourself feel better:

• Fill your water bottle. Sip water or fruit juice to prevent dehydration. Resist any temptation to treat your hangover with more alcohol. It'll only make you feel worse.
• 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.
• Take a pain reliever. A standard dose of a pain reliever you can buy without a prescription may ease a headache. But be careful about using these medicines with alcohol. Aspirin and ibuprofen (Advil, Motrin IB, others) can irritate your stomach. The combination of alcohol and acetaminophen (Tylenol, others) can cause serious liver damage.
• Go back to bed. If you sleep long enough, your hangover may be gone when you awaken.

Many alternative remedies are marketed for hangovers. But studies haven't found any natural remedies that consistently or effectively improve hangover symptoms.

Talk with your healthcare professional before trying any alternative medicine. Keep in mind that natural doesn't always mean safe. Your healthcare professional can help you understand possible risks and benefits before you try a treatment.