A typical hangover lasts up to 24 hours, but a bad one can stretch well beyond that. Some people report feeling rough for 48 to 72 hours after heavy drinking, depending on how much they consumed, what they drank, and how efficiently their body processes alcohol. The NIAAA notes that hangover symptoms “can last 24 hours or longer,” and several biological factors determine where you fall on that timeline.
What Determines How Long It Lasts
Your hangover duration comes down to how quickly your body clears alcohol and its toxic byproducts. When you drink, your liver converts alcohol into a compound called acetaldehyde, which is significantly more toxic than the alcohol itself. A second enzyme then breaks acetaldehyde down into harmless substances. If that second step works efficiently, hangover symptoms resolve faster. If it doesn’t, acetaldehyde lingers in your system and keeps you feeling sick longer.
This isn’t purely about how much you drank. Genetics play a major role. Some people carry a less active version of the enzyme responsible for clearing acetaldehyde. Research has shown that individuals with this genetic variation experience hangovers after significantly less alcohol than those with fully active enzymes, and their symptoms tend to be more severe. This variation is particularly common in people of East Asian descent, but enzyme efficiency varies across all populations.
Your immune system also gets involved. About nine hours after you stop drinking, your body ramps up production of inflammatory signaling molecules, the same ones activated when you’re fighting an infection. That immune response contributes to the fatigue, brain fog, and general misery of a hangover. By around 13 hours, those levels start dropping. But during that inflammatory window, your body is essentially treating the aftermath of alcohol like a low-grade illness, and for heavy drinking episodes, that process takes longer to resolve.
Why Some Hangovers Stretch Past 24 Hours
A hangover that drags into a second or third day usually involves one or more compounding factors. The most straightforward is volume: the more you drank, the longer it takes your liver to process everything. Your liver can only metabolize roughly one standard drink per hour, so a night involving 10 or more drinks means your body is still clearing alcohol well into the next day, before recovery even truly begins.
What you drank matters too. Dark liquors like brandy, red wine, and rum contain high levels of congeners, chemical byproducts of fermentation that give these drinks their color and flavor. Your body has to break down congeners alongside the alcohol itself, and sometimes those two processes compete for the same metabolic pathways. The result is that both alcohol and its byproducts stay in your system longer. Congeners also trigger the release of stress hormones that fuel inflammatory responses, adding fatigue and body aches on top of the standard symptoms. Vodka and beer sit at the low end of the congener scale, which partly explains why darker spirits tend to produce worse hangovers.
Dehydration amplifies everything. Alcohol suppresses the hormone that tells your kidneys to retain water, so you lose fluids faster than normal while drinking. That dehydration contributes to headaches, dizziness, and fatigue. Rehydrating helps with those specific symptoms, but it won’t speed up the breakdown of alcohol itself. Other symptoms, particularly nausea, sensitivity to light, and mental fog, generally persist until your body finishes processing all the alcohol and acetaldehyde, which can take a full 24 hours or more regardless of how much water you drink.
Age Makes a Real Difference
If hangovers seem to hit harder and last longer than they used to, you’re not imagining it. As you age, your total body water decreases, which means the same amount of alcohol produces a higher blood alcohol concentration than it would have in your twenties. Your liver also becomes slower at eliminating alcohol from your system. Harvard Health notes that after drinking identical amounts, older adults end up with higher blood alcohol levels than younger people, purely because of these physiological changes. The practical effect is that a night of drinking that would have produced a manageable morning-after at 25 can leave you wiped out for two days at 45.
Rehydrating: Water vs. Electrolytes
Plain water restores lost fluid but doesn’t replace the sodium, potassium, and other electrolytes you lose from alcohol’s diuretic effect. Electrolyte drinks use a specific ratio of sugar and salt that pulls fluid into your bloodstream faster than water alone, which can relieve dehydration symptoms more quickly. That said, rehydration primarily addresses headache, dry mouth, and dizziness. The deeper hangover symptoms tied to acetaldehyde breakdown and inflammation will still take roughly 24 hours to fully clear, no matter what you’re sipping.
Eating before and during drinking slows alcohol absorption, which gives your liver more time to keep up with processing. This won’t prevent a hangover entirely after heavy drinking, but it can reduce the peak severity, which in turn shortens the tail end of symptoms.
When It’s More Than a Hangover
A hangover is miserable but not dangerous on its own. Alcohol poisoning is. The two can look similar in the early hours, but certain signs point to a medical emergency rather than a rough morning. These include seizures, breathing that drops below eight breaths per minute, gaps of more than 10 seconds between breaths, blue or pale skin, low body temperature, and inability to be woken up. Persistent vomiting combined with confusion is another red flag. A hangover generally improves as time passes. Alcohol poisoning gets worse, and it requires emergency medical attention.
If your hangover symptoms haven’t improved at all after 48 hours, or if you notice yellowing skin, persistent rapid heartbeat, or symptoms that feel distinctly different from your usual post-drinking experience, something beyond a standard hangover may be going on.