Hangover symptoms typically include headache, fatigue, nausea, thirst, muscle aches, sensitivity to light and sound, anxiety, irritability, and difficulty concentrating. They begin as your blood alcohol level drops toward zero and last roughly 12 hours from when you wake up, though the full duration from your last drink averages about 18 hours, with most people falling in a 14- to 23-hour window.
The Full List of Symptoms
Researchers use a 13-item scale to measure hangover severity, and the items on it paint a thorough picture of what you might experience. The core physical symptoms are intense thirst, headache, fatigue, weakness, nausea, vomiting, and sweating more than usual. On the cognitive and emotional side, you may have trouble concentrating, feel anxious or depressed, and notice heightened sensitivity to light and sound. Some people also experience trembling or shaking and disrupted sleep. Increased blood pressure, stomach pain, vertigo, and muscle aches round out what the National Institute on Alcohol Abuse and Alcoholism identifies as typical complaints.
Not everyone gets every symptom, and the mix varies from person to person and even from one drinking occasion to the next. But dehydration-related symptoms (thirst, headache, fatigue) and stomach-related symptoms (nausea, pain, vomiting) are among the most common.
Why Your Head Pounds and Your Body Aches
Several overlapping processes cause hangover symptoms, not just one. Dehydration is the most familiar culprit. Alcohol suppresses a hormone that tells your kidneys to retain water, so you lose more fluid than you take in. That mild dehydration contributes directly to thirst, fatigue, and headache.
Your body also mounts an inflammatory response to alcohol. Levels of specific immune signaling molecules, particularly IL-6 and IL-10, rise significantly the day after heavy drinking. These are the same types of molecules your body produces when you’re fighting off an infection, which is why a hangover can feel oddly similar to being sick: achy, foggy, and run down. The immune system communicates with the brain through hormonal pathways and the vagus nerve, ramping up inflammation centrally and contributing to that overall feeling of malaise.
The Toxic Byproduct Your Liver Produces
When your liver breaks down alcohol, it first converts it into an intermediate substance called acetaldehyde before converting that into a harmless compound called acetate. Acetaldehyde is reactive and toxic. At higher concentrations it causes a rapid pulse, sweating, skin flushing, nausea, and vomiting. If your liver can’t clear acetaldehyde fast enough, it builds up, and your symptoms get worse.
Genetics play a real role here. A significant percentage of people of East Asian descent carry a variant in the gene for the enzyme that clears acetaldehyde. This variant slows the process, leading to more acetaldehyde buildup and more severe hangovers. Research on Asian Americans found that carrying this gene variant accounted for meaningful additional variability in hangover severity even after controlling for gender and drinking history. The upside, if you can call it that, is that these worse hangovers appear to be partly protective against developing problematic drinking patterns.
Why Your Stomach Rebels
Alcohol directly irritates the lining of your stomach and triggers extra acid production. This combination can cause nausea, vomiting, stomach pain, heartburn, and loss of appetite. In the short term, a single episode of heavy drinking inflames the stomach lining enough to make absorbing nutrients from food less efficient, which can add to the general weakness and fatigue you feel the next day. Acidic digestive juices may also push up into the esophagus, producing that uncomfortable burning sensation in your chest.
How Alcohol Wrecks Your Sleep
One of the more underappreciated hangover mechanisms is what alcohol does to sleep quality. Alcohol acts as a sedative initially: you fall asleep faster, and you spend more time in deep slow-wave sleep during the first half of the night. But it suppresses REM sleep (the restorative, dream-heavy phase) and delays when REM sleep kicks in. Then, in the second half of the night, the pattern flips. Sleep becomes fragmented, with more wakefulness and lighter sleep stages. You tend to wake up earlier than you otherwise would.
The result is that even if you were in bed for eight hours, the actual quality of your sleep was poor. This directly feeds the fatigue, difficulty concentrating, and irritability that define a hangover morning. It’s not just that you’re dehydrated or inflamed. You’re also genuinely sleep-deprived.
The Anxiety and Restlessness Component
Hangover anxiety is common enough that it has its own nickname online (“hangxiety”), and there’s a physiological reason for it. While you’re drinking, alcohol enhances calming activity in the brain, making you feel relaxed and socially at ease. But the brain quickly adjusts to counterbalance that effect. When alcohol leaves your system, the rebound overshoots: you end up feeling more restless and anxious than you were before you started drinking. This is essentially a mini-withdrawal, and it explains why some people wake up the morning after drinking with a racing heart and a sense of dread that seems completely out of proportion to anything that actually happened.
What Makes Some Hangovers Worse
Beyond how much you drink, the type of alcohol matters. Darker spirits and red wine contain higher levels of compounds called congeners, which are byproducts of fermentation and aging. These include substances like methanol, which your liver eventually converts to formaldehyde and then formic acid, both of which are toxic. Distilled beverages can concentrate methanol further, which may explain why bourbon or brandy tends to produce worse hangovers than vodka or gin at equivalent alcohol doses. Fusel alcohols, another category of congener, can compound the effects of alcohol and acetaldehyde.
Other factors that worsen symptoms include drinking on an empty stomach (which speeds alcohol absorption), not drinking water alongside alcohol, smoking while drinking, and simply having a higher total alcohol intake. Your body size, sex, overall health, and genetic enzyme profile all shift the threshold at which symptoms become significant.
Timeline: When Symptoms Peak and Fade
Hangover symptoms begin as your blood alcohol concentration approaches zero, not while you’re still intoxicated. For most people who stop drinking late at night, this means symptoms start in the early morning hours and peak sometime in the first half of the day. From the moment you wake up, you can expect roughly 12 hours before symptoms fully resolve. Measured from your last drink, the average total duration is about 18 hours, with the typical range spanning 14 to 23 hours.
Symptoms don’t all follow the same curve. Nausea and stomach pain often improve faster once you’re able to eat and hydrate. Fatigue and difficulty concentrating can linger into the evening, especially if the sleep disruption was severe. The anxiety component tends to peak in the morning and gradually ease as your brain chemistry rebalances over the course of the day.