How long does a hangover last?

Between 14 and 23 hours in the research that measured it, averaging about 18 hours from your last drink, which works out to roughly 12 hours after waking up. Most are gone within a day. Longer ones happen, and a hangover that is still going strongly after 24 hours is worth taking more seriously than a rough morning.

It begins as your blood alcohol approaches zero, not when you stop drinking. That is why a heavy night often produces a hangover that starts mid or late morning: the alcohol is still clearing at breakfast, and the hangover only arrives behind it. It also means a bigger night pushes the start later as well as making the whole thing worse.

Three ordinary explanations before anything exotic. Sleep debt, which the research links to hangover severity more strongly than the amount drunk in some samples, and which takes more than one night to repay. A very large dose, which lengthens everything. And the fact that what people call a two-day hangover is often the second day of a sleep deficit rather than the hangover itself. Persistent vomiting, severe abdominal pain, or confusion are different, and are reasons to see a doctor.

It does not shorten the alcohol clearance, but sleep is the factor with the clearest relationship to how bad the hangover is. In a study of 578 students, shorter total sleep time was associated with more severe hangovers, while total alcohol consumed did not correlate significantly with severity or duration. Curiously, those who slept longer reported longer but milder hangovers. So sleep changes the experience considerably, and the timetable much less.

Reported hangovers beyond 24 hours exist but are the tail rather than the norm, and the evidence on them is thin. Before assuming a two-day hangover, account for accumulated sleep loss, a second late night, dehydration you never corrected, and the fact that a very heavy session starts its hangover clock later in the first place. If symptoms genuinely persist for days, that is a conversation with a doctor rather than a remedy.

It changes how bad it is more than how long. Darker drinks carry more congeners, the flavour compounds that come with the colour, and at the same dose they produce measurably worse hangovers than clear spirits. In the trial that tested bourbon against vodka, next-day cognitive impairment was identical between them, so switching to clear spirits may make you feel better without making you any less impaired.

Roughly, but not reliably enough to act on. The hangover typically arrives as blood alcohol reaches zero, so feeling terrible is a weak signal that the alcohol has cleared. It is far too weak to drive on: hangover and blood alcohol overlap in both directions, and every year people are caught over the limit at breakfast while feeling merely hungover. Estimate the alcohol separately and never drive after drinking.

No. Nothing shortens a hangover, and no drink, pill, drip, food, or shower changes its duration. What you can do is treat the individual symptoms while it runs: fluids, food when your stomach agrees, painkillers within their label doses, and more sleep. The only lever with a real effect on the next hangover is how much you drink before it.