Some people can drink the same amount as their friends and feel dramatically worse the next morning. That’s not imagined, and it’s not about toughness. Hangover severity is shaped by a mix of genetics, body composition, age, sleep quality, gut health, and what you’re drinking. Understanding which factors apply to you can explain why hangovers hit you harder.
Your Genes Control How Fast You Process Alcohol
When you drink, your body breaks alcohol down in two steps. First, enzymes in your stomach and liver convert alcohol into a toxic compound called acetaldehyde. Then a second enzyme, ALDH2, converts that acetaldehyde into harmless acetic acid. The speed and efficiency of each step varies enormously from person to person based on genetics.
The most well-studied variation involves the ALDH2 gene. A point mutation common in East Asian populations produces an inactive form of ALDH2 that causes acetaldehyde to pile up in the body after drinking. People who carry one copy of this variant break down acetaldehyde significantly more slowly, leading to higher blood levels of this toxin. The result: flushing, pounding heartbeat, headache, and nausea, sometimes after just one drink. If you turn red when you drink, this is likely why your hangovers feel disproportionate to how much you consumed.
But ALDH2 isn’t the only genetic variable. How much of the first enzyme (alcohol dehydrogenase, or ADH) you produce in your stomach also matters. Men typically have higher gastric ADH activity than women, which means more alcohol gets broken down before it ever reaches the bloodstream. Women, by contrast, tend to have higher liver ADH activity, which speeds up elimination once alcohol is already circulating. These differences create different timelines for how alcohol and its toxic byproducts move through your system.
Body Composition Changes the Equation
Alcohol dissolves in water, not fat. So your blood alcohol level after a given number of drinks depends heavily on how much water is in your body. Two people who weigh the same amount can reach very different blood alcohol concentrations if one carries more body fat and less water. This is one reason women, who on average carry a higher percentage of body fat and lower percentage of body water than men, often reach higher blood alcohol levels from identical drinks.
This also means that changes in your own body composition over time, like gaining fat or losing muscle, can shift how intensely you feel alcohol and its aftermath, even if your drinking habits haven’t changed.
Age Makes Hangovers Worse
If hangovers seem to get worse every year, they probably are. The activity of the key enzymes that metabolize alcohol, including alcohol dehydrogenase, acetaldehyde dehydrogenase, and a liver enzyme called CYP2E1, all diminish with age. At the same time, your body’s total water volume decreases. Both changes mean the same number of drinks produces higher blood alcohol concentrations that linger longer. Your liver simply processes alcohol less efficiently than it did a decade ago.
Alcohol Triggers an Inflammatory Response
A hangover isn’t just about dehydration or toxin buildup. It’s also an inflammatory event. Research has found that hangover severity correlates directly with blood levels of inflammatory markers, particularly IL-6, TNF-alpha, and C-reactive protein (the same marker doctors check for general inflammation). Notably, at four hours after drinking, it was the blood alcohol concentration itself, not acetaldehyde, that was associated with elevated IL-6 levels. This suggests alcohol directly provokes inflammation regardless of how efficiently you metabolize it.
If you already have a baseline of higher inflammation from poor sleep, stress, a sedentary lifestyle, or an inflammatory condition, you may be starting from a higher set point. Adding alcohol on top of that can push your inflammatory response into territory that feels much worse than what your friends experience.
Your Gut Health Plays a Bigger Role Than You Think
Researchers at Rush University have proposed that the gut-brain axis is a key driver of hangover symptoms. Alcohol disrupts the balance of bacteria in your intestines, increasing pro-inflammatory species and decreasing anti-inflammatory ones. It also reduces short-chain fatty acids, compounds that help maintain the integrity of your intestinal lining.
When that lining becomes “leaky,” bacterial toxins escape into the bloodstream and trigger a systemic inflammatory response, elevating the same cytokines (IL-6, TNF-alpha) linked to hangover severity. If you already have poor gut health from a low-fiber diet, frequent antibiotic use, or regular drinking, your gut barrier may be more vulnerable to alcohol’s effects, amplifying the inflammatory cascade that makes you feel terrible the next day.
Alcohol Wrecks Your Sleep Architecture
You might pass out quickly after drinking, but the sleep you get is fragmented and low-quality. Alcohol initially acts as a sedative: it shortens the time it takes to fall asleep and increases deep slow-wave sleep during the first half of the night. But as your body processes the alcohol, a rebound effect kicks in during the second half. REM sleep increases, you wake up more frequently, and overall sleep time drops.
A naturalistic study found that the number and duration of nighttime awakenings were directly related to hangover severity ratings the next day. Worse sleep also correlated with poorer cognitive performance, including slower reaction times and reduced attention. Total hangover severity accounted for about 11% of the variance in a cognitive performance task. So a significant portion of what feels like a “hangover” is actually the downstream effect of badly disrupted sleep. If you’re already a light sleeper or have irregular sleep patterns, alcohol compounds the problem.
What You Drink Matters
Not all alcoholic drinks produce equal hangovers. Darker spirits like bourbon, brandy, and heavily flavored rums contain high levels of congeners, chemical byproducts of fermentation and aging. Some Jamaican rums, for example, contain congener concentrations exceeding 9,000 milligrams per liter of pure alcohol. These compounds are independently toxic and add to the metabolic burden your body faces the morning after. Lighter options like vodka and gin contain far fewer congeners. Switching what you drink won’t eliminate hangovers, but it can meaningfully reduce their severity.
Dehydration and Nutrient Loss
Alcohol suppresses vasopressin, a hormone that tells your kidneys to retain water. It does this by interfering with calcium signaling in the nerve terminals that release vasopressin. With less vasopressin circulating, your kidneys let more water pass through as urine. This is why you urinate so frequently when drinking and wake up parched. The resulting dehydration contributes to headache, fatigue, and dizziness.
Alcohol also depletes several key nutrients. The vitamins most commonly affected are folate, B6, thiamine (B1), and vitamin A. Alcohol interferes with the absorption, storage, metabolism, and activation of these vitamins. Thiamine and B6 are essential for energy metabolism and nervous system function, so even a temporary dip can worsen the fatigue and brain fog you feel during a hangover. People who drink frequently may carry chronic low-level deficiencies that make each hangover feel progressively worse.
Medications Can Amplify the Effects
If you take any regular medication, it may be making your hangovers worse. According to the National Institute on Alcohol Abuse and Alcoholism, a wide range of common drugs interact with alcohol, including allergy medications like diphenhydramine and cetirizine, anti-anxiety medications like lorazepam and alprazolam, ADHD medications, and common pain relievers like naproxen and celecoxib. Antihistamines combined with alcohol increase drowsiness and dizziness. Anti-inflammatory pain relievers mixed with alcohol raise the risk of stomach bleeding and liver damage. Even some herbal supplements like kava can cause liver damage when combined with alcohol.
These interactions don’t just create new problems. They can intensify the standard hangover symptoms you’d experience anyway, making the same amount of alcohol feel significantly worse than it would without the medication.
Putting It Together
Hangover susceptibility isn’t one thing. It’s the sum of your genetics, your sex, your age, your body composition, your gut health, your sleep quality, your medications, and even your drink of choice. Some of these you can’t change: your enzyme genetics are fixed, and aging only goes one direction. But several factors are modifiable. Improving gut health through diet, choosing lower-congener drinks, staying hydrated while drinking, protecting your sleep, and checking whether your medications interact with alcohol can all meaningfully shift how you feel the morning after.