What happens to your body during a hangover?

The morning after a big night out often feels like waking up in a body that is not fully yours. The light is too harsh, sounds feel louder than usual, and even simple movements can feel heavy. Your mouth is dry, your heart might beat a little faster, and there is a strange fog pressing behind your eyes. This familiar, miserable state is a hangover, but underneath the headache and nausea, there is a complex story unfolding. A hangover is your body trying to clear a toxic substance, repair irritated tissues, rebalance your chemistry, and catch up on work it could not fully do while you were drinking.

To understand what happens to your body during a hangover, it helps to start with how your body handles alcohol in the first place. The moment you drink, alcohol is absorbed through the stomach and small intestine and then carried into your bloodstream. Your body recognises alcohol as a toxin that cannot be stored safely, so it gives your liver top priority to deal with it. The liver breaks ethanol down into acetaldehyde, a substance that is actually more toxic than alcohol itself. Under light drinking conditions, your liver can quickly convert acetaldehyde into acetate, which is less harmful and can be processed and removed. When you drink heavily or over a long period of time, this system becomes overloaded. Acetaldehyde and other byproducts linger longer than they should, irritating tissues and contributing to that sick, poisoned feeling that defines a hangover.

While all of this is happening, your brain is quietly being pushed away from its usual balance. Alcohol affects neurotransmitters, the chemical messengers that shape your mood, thinking, and level of alertness. During drinking, alcohol enhances calming signals and dampens some of the brain activity that keeps you cautious and controlled. That is what makes you feel more relaxed and more uninhibited. The problem is that your brain does not simply return to neutral once the alcohol wears off. It often rebounds too far in the opposite direction. The calming signals drop, stress related chemicals and inflammatory messengers rise, and the result can be a wired yet exhausted state. You might feel restless but tired, anxious for no clear reason, or strangely emotional. The headache you feel is not only about dehydration. It is also influenced by changes in blood vessels, brain chemistry, and low level inflammation.

Dehydration still matters, though it is only one piece of the puzzle. Alcohol is a diuretic, which means it encourages your kidneys to produce more urine. Even if you drank a lot of fluid in the form of mixed drinks or beer, your body loses more water and electrolytes than usual. By the time you crawl into bed, you may already be mildly dehydrated. The next morning, this shows up as thirst, dry mouth, dizziness when you stand up, and a sense that your head is pounding from the inside. Your blood volume may be slightly reduced, which affects blood flow to your brain and other organs. This is part of why drinking water or an electrolyte rich drink in the morning can help you feel a little more human, even though it cannot instantly reverse everything else.

Your digestive system also plays a big role in how a hangover feels. Alcohol irritates the lining of the stomach and intestines and increases acid production. This is why even a moderate amount of drinking can leave some people with burning discomfort in the upper abdomen, queasiness, or outright vomiting. Your stomach muscles and intestines may be more sensitive and more reactive the next day. Eating greasy or very heavy food after a night out can sometimes make those symptoms worse, especially if your stomach lining is already irritated. At the same time, alcohol interferes with normal blood sugar regulation. The liver is so busy dealing with alcohol that it does a poorer job of keeping your blood sugar stable. You might wake up shaky, sweaty, or weak. You may feel unbelievably hungry, yet the idea of food does not sound appealing. This combination of low blood sugar and digestive irritation is one of the reasons a simple, balanced meal that is gentle on the stomach is often more helpful than a huge, oily breakfast.

Running alongside all these changes is your immune system, which treats heavy drinking a little like an attack. Alcohol intake, especially in large amounts, can trigger the release of cytokines, the signalling molecules your body also uses when you are fighting an infection. In a real illness, this process helps you recover. After a long night out, it turns into muscle aches, low grade feverish sensations, and a general feeling of being unwell. You might feel as if you are coming down with a flu that never quite arrives. This is your immune system responding to irritation and damage and is a big reason why hangovers feel so all consuming. It is not only your head or your stomach that is affected. Your whole body is participating in the repair.

Sleep, which should be your biggest ally in recovery, is also disrupted by alcohol. Many people fall asleep more quickly when they drink, which can trick you into thinking that alcohol helps with rest. Behind the scenes, it fragments your sleep, especially in the second half of the night. Alcohol reduces the amount of deep restorative sleep and suppresses REM sleep for part of the night, then causes REM to rebound in a shallow, restless way as your blood alcohol level drops. You may wake earlier than usual, toss and turn, or have vivid, unsettling dreams. When you open your eyes in the morning, you have not only biochemical chaos in your body but also genuine sleep debt. This combination makes the fatigue of a hangover feel unusually heavy, as if your mental energy has been drained from several directions at once.

Your hormones are caught up in the aftermath too. Alcohol can temporarily increase heart rate and blood pressure and interfere with hormones that regulate how your body holds on to water. That disruption ties back into dehydration and the flushed, racing feeling some people experience both during drinking and the next day. Stress hormones like adrenaline can remain elevated into the morning, feeding anxiety, irritability, and a sense that your body is on edge. For some people, the emotional part of a hangover is harder to bear than the physical discomfort. They feel guilty, panicky, or unusually low in mood. This emotional crash is not a character flaw. It is the result of brain chemistry, hormone shifts, poor sleep, and physical stress colliding all at once.

Not all drinks affect you in the same way, even if the amount of pure alcohol is similar. Alcoholic beverages contain congeners, which are byproducts of fermentation such as other alcohols, aldehydes, and tannins. Darker drinks like whiskey, rum, brandy, and red wine tend to have higher levels of congeners. Lighter coloured drinks like vodka or some gins usually contain fewer. Research suggests that drinks with more congeners may lead to more intense or longer lasting hangovers. This is why you might feel much worse after a night of dark spirits compared to the same number of clear spirit drinks, even if the total alcohol content matches. What is in your glass, not just how much, can shape what your next morning looks like.

Genetics add another layer of complexity. Some people have inherited variations in the enzymes that process alcohol and acetaldehyde. Many East Asians, for example, carry a variant that causes acetaldehyde to accumulate more easily. This leads to flushing, rapid heartbeat, headache, and nausea even with small amounts of alcohol. For these individuals, the body sends stronger, earlier warning signals. Hangovers can feel harsher and may arrive after fewer drinks. Those reactions are not random or dramatic. They are your body drawing an urgent boundary, saying that this substance is especially stressful for your system.

Knowing all of this, what can you actually do when you are moving slowly around your home, clutching a glass of water and wondering why you thought that last drink was a good idea? The truth is there is no magic cure that can instantly reset your liver, calm inflammation, replace lost sleep, and stabilise all your hormones at once. Your body still has to go through its own process of metabolising the alcohol and cleaning up after it. However, you can remove unnecessary obstacles and support that process instead of fighting it. Hydrating steadily with water or electrolyte drinks helps your circulation and your kidneys clear waste more comfortably. Eating gentle, nourishing food, like toast with eggs, oatmeal, or a simple soup, gives your body energy without overwhelming your stomach. Resting your nervous system by avoiding extra stress, loud environments, or heavy commitments lets your body focus on repair.

The more powerful changes, though, usually happen before the hangover ever shows up. Your rituals around drinking can soften what your body experiences the next day. Eating a proper meal before drinking slows down alcohol absorption and gives your liver more time to work through what arrives. Sipping more slowly instead of stacking drinks back to back reduces the peak level of alcohol in your blood. Alternating alcoholic drinks with glasses of water not only decreases dehydration but also naturally reduces how much alcohol you consume over the night. Choosing drinks with fewer congeners and setting a personal cutoff time so that alcohol does not dominate the second half of your sleep can make a noticeable difference to how you feel in the morning. These are small decisions that protect tomorrow, not just tonight.

There is also a quieter, more reflective side to hangovers that many of us prefer not to look at. If your hangovers feel severe even after a modest amount of alcohol, or if they are becoming frequent, it can be a signal that your body is struggling with your current drinking patterns. If you ever notice worrying symptoms such as confusion, chest pain, difficulty breathing, or repeated vomiting, that is a medical red flag and needs urgent attention. Beyond emergencies, persistent, heavy hangovers might be nudging you to reassess the role alcohol plays in your social life, stress management, or sense of identity. Talking with a healthcare professional, therapist, or support group about your relationship with alcohol is a form of self care, not a confession of failure.

In the end, a hangover is your body speaking in a language of symptoms. Headache, nausea, fatigue, anxiety, and sensitivity to light and sound are messages, not random punishments. They are updates from your liver, your brain, your gut, your immune system, and your hormones, all reporting on how last night went for them. When you start to understand this, the story shifts. You can still choose to drink, but you do so with a clearer view of the cost your body pays to keep up with you. That understanding opens the door to gentler rituals, kinder mornings, and sometimes entirely new ways of celebrating that allow you to wake up in a body that feels more like home.