Hangovers are rough. And the more you drink the night before, the more severe your hangover symptoms might feel the morning after.

Most of the time you just need to drink water, eat some food, and walk it off. But if you’ve had too much to drink, you may be harming your body and need to see your doctor for treatment.

Let’s look at how to tell the difference between a mild, temporary hangover that you can treat at home and one that may need some extra medical attention.

Each of these 10 common symptoms stems from a physiological response to the presence of alcohol in your digestive and urinary systems, especially your stomach, kidneys, and bloodstream.

Alcohol expands (dilates) your blood vessels. At first, this can be beneficial, making you feel relaxed as your blood pressure is lowered.

But after a few drinks, your heart starts pumping faster, and the blood vessels can’t expand enough to accommodate all the blood. This additional pressure can cause headaches. Blood vessel dilation has also been linked to migraines.

Alcohol does a double whammy on your tummy: A few drinks can not only make your stomach produce more acid, but also keep your stomach from emptying. This can make you feel sick and induce vomiting.

Alcohol can direct heavier blood flow to areas in your pancreas known as islets. This causes your pancreas to make more insulin, which can make your blood sugar drop. This can make you feel exhausted, tired, and weak.

Alcohol can interfere with your sleep cycle.

When you drink, your body adjusts to the alcohol in your system in order to maintain a normal 8(ish)-hour cycle of sleep. But your body generally eliminates all the alcohol from your system after five to six hours, yet still remains adjusted to the presence of alcohol.

This “rebound effect” interrupts deep, rapid-eye-movement (REM) sleep, which can make you feel much more tired the next day.

Alcohol’s a diuretic. This means it makes you pee more often than usual, which can quickly drain your body of fluid as well as important minerals and vitamins.

As you lose fluid through frequent urination, you’ll become increasingly dehydrated and extremely thirsty as a result, especially if you’re drinking in a hot environment that’s making you sweat, too.

Alcohol is known to increase your heart rate. The more you drink, the more your heart will respond.

A 2018 study of 3,000 attendees of Oktoberfest in Munich, Germany, found that high levels of alcohol, especially in younger people, are associated with symptoms like sinus tachycardia. This is a heart rate over 100 beats per minute, which is well above the average heart rate.

The study also suggested that heart rate increases as you drink more alcohol, and these increases can raise your risk of arrhythmia, an irregular heartbeat.

Dizziness is a common symptom of the dehydration that comes with a hangover. When you’re dehydrated, your blood pressure drops, which limits blood flow to your brain and causes dizziness.

Drinking alcohol, especially if you’re already dehydrated or becoming dehydrated, can make it harder to focus on certain tasks, react during situations, and make decisions.

The fluctuations in blood sugar that accompany drinking can lead to negative moods, which might include anxiety and anger as well as mood instability. This can occur both during and after drinking.

Drinking can also affect your mood if you already have a mental health condition or use alcohol as a coping mechanism for your emotional health. A 2017 study found that many people report feeling more aggressive or even feeling an overwhelming amount of emotions when they drink, especially if they had some dependence on alcohol.

You may feel much less alert, less able to remember things, and less able to make logical decisions when you’re hungover. A 2017 study found that these aspects of cognitive function were all highly impacted during a period of hangover symptoms.

First: Drink water! Many hangover symptoms result from dehydration.

Here are a few other tips for snapping back quickly from a hangover:

  • Eat. Alcohol can drop your blood sugar levels. Fill up on carbohydrates, like crackers or bread, to normalize your blood sugar. Eat foods packed with vitamins, such as eggs, fish, nuts, and avocados, to help replenish depleted nutrients. Can’t keep food down? Sip on a thin vegetable broth.
  • Take pain medication (but not Tylenol). Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil) or aspirin, can help take the edge off aches and pains. Just avoid acetaminophen (Tylenol). It can cause liver damage when taken in tandem with alcohol.
  • Don’t try the “hair of the dog” method. Having alcohol when you’re hungover may make your symptoms worse or just dull your symptoms briefly before they come right back.

Check out these additional science-backed solutions for a hangover.

How much you need to drink to cause a hangover depends on many factors. Some people may only need one or two drinks to get drunk and feel hungover the next day. Others can drink far more and feel minimal symptoms afterwards.

You may build a tolerance to alcohol if you drink enough consistently. This occurs when your body learns to adjust to the presence of alcohol and produce more enzymes to break down alcohol in your system.

Other factors that affect how much alcohol you can tolerate include:

  • Age. Your body may become less able to metabolize alcohol as you get older. This is because your body contains less total water volume to dilute the alcohol in your system.
  • Genetics. Some people have a gene that makes their body less able to metabolize certain substances in alcohol, so they may not even be able to have one drink before experiencing uncomfortable symptoms like skin flushing or stuffy nose.
  • Weight. The heavier you are, the longer it may take for you to feel the effects of alcohol. This is because you have more body volume through which alcohol can diffuse.

Drinking too much can cause alcohol poisoning. This affects many of your body’s normal functions, such as breathing, temperature regulation, and heart rate. Alcohol poisoning can be deadly or have serious long-term consequences.

Seek emergency medical attention if you or someone you’re drinking with exhibits any of the following symptoms:

  • feeling disoriented
  • throwing up
  • having seizures
  • having pale, bluish skin
  • breathing slowly (inhaling and exhaling less than eight times per minute)
  • breathing irregularly (going 10 seconds or more between each breath)
  • feeling abnormally cold
  • losing consciousness and unable to wake up

Drink water and eat food to dispel your hangover blues.

It’s possible to reduce hangover symptoms by eating food and drinking plenty of water while you’re consuming alcohol, but there’s only so much you can do to avoid one.

Limiting how much alcohol you drink at one time is the most effective way to minimize the possibility of a hangover. And try to drink with people around you. It’s a good idea to have someone on hand to let you know if you’re perhaps consuming too much.