Hangover Timeline: What Happens in Your Body, Hour by Hour

A hangover isn’t a single event. Researchers describe it as a cascade of overlapping processes — alcohol metabolism, dehydration, sleep disruption, and inflammation — that build and resolve on different schedules. This is a neutral walk through that timeline, drawing on what the published literature does and doesn’t show. It is education, not a treatment plan.

These statements have not been evaluated by the Food and Drug Administration or Health Canada. This product is not intended to diagnose, treat, cure, or prevent any disease. Consult your healthcare provider before use.

When does a hangover actually start?

The symptoms you feel the next morning are set in motion while you’re still drinking, but they tend to surface as blood alcohol falls toward zero — usually several hours after your last drink. For a deeper look at the underlying drivers, see what causes a hangover.

The timeline below uses approximate windows. Real timing varies widely with how much you drank, how fast, your size, your genetics, and your sleep — so treat the hours as a rough map, not a stopwatch.

During drinking (roughly 0–4 hours)

What the literature describes happening in this window:

Ethanol is absorbed from the stomach and small intestine, typically within tens of minutes per drink.
Blood alcohol rises. Alcohol potentiates GABA-A receptors, which is associated with the sedation and relaxation people feel early in a session.
In the liver, the enzyme alcohol dehydrogenase (ADH) converts ethanol to acetaldehyde, and aldehyde dehydrogenase (ALDH) converts acetaldehyde to acetate. The body clears roughly one standard drink per hour on average; drinking faster than that lets alcohol accumulate.
Alcohol suppresses the hormone vasopressin, so the kidneys excrete more water and electrolytes — the start of the dehydration people notice later.

At this stage you typically feel the effects of alcohol itself, not a hangover.

Late night and during sleep (roughly 4–8 hours after your last drink)

Blood alcohol begins to decline; acetaldehyde concentrations are relatively high while the body works through the backlog.
GABA-A receptor activity begins to adapt to the alcohol’s presence — a neuroadaptation that researchers link to the rebound effects felt later.
Alcohol disrupts sleep architecture: it can shorten the time to fall asleep but suppresses REM sleep in the first half of the night, which is part of why post-drinking sleep is often unrefreshing.

This is the window where you’re asleep but the underlying processes are most active.

Early morning (roughly 6–10 hours after drinking)

Blood alcohol is often cleared by now, depending on how much you drank.
The GABA-A neuroadaptations from earlier can manifest as central-nervous-system rebound — sometimes felt as anxiety, restlessness, or sensitivity to light and sound. This is the “hangxiety” many people describe.
REM rebound can bring fragmented sleep and vivid dreams.
Inflammatory signaling rises: studies report increases in cytokines associated with the immune response to alcohol, which researchers connect to the general malaise of a hangover.

Peak symptoms (roughly 8–14 hours after your first drink)

For many people the worst symptoms arrive after blood alcohol has already returned to zero — often mid-morning to early afternoon. A frequently cited observation in hangover research is that symptom severity tends to peak around the time blood alcohol reaches zero, not while it’s highest.

Here’s a neutral map of common symptoms and the mechanisms researchers most often associate with them:

Symptom	Mechanisms researchers associate with it	Typical peak
Headache	Dehydration, inflammatory signaling, blood-vessel changes	Morning
Nausea	Gastric irritation, inflammatory mediators	Morning–midday
Anxiety / hangxiety	GABA-A rebound, stress-hormone elevation	Morning
Fatigue	Disrupted sleep, residual metabolic load	All day
Light / sound sensitivity	CNS hyperexcitability associated with GABA rebound	Morning
Brain fog	Dehydration, inflammatory signaling, poor sleep	Morning–midday

These associations are how the symptoms are commonly explained in the literature; they are not a claim that any product changes them.

Recovery (roughly 12–36 hours)

GABA-A receptor activity gradually normalizes; heavier sessions are generally associated with longer recovery.
Inflammatory signaling resolves as immune activation settles.
Hydration and electrolytes recover as you eat and drink normally.
Sleep typically normalizes the following night.

Factors that the research associates with a longer or harder hangover include the amount consumed, age, genetics (for example, people who carry the ALDH2*2 variant clear acetaldehyde more slowly), poor sleep, and dehydration. There’s no shortcut that reliably skips the timeline — time is the one factor that always applies.

How long does a hangover last?

Most hangovers resolve within about 24 hours, and many are largely gone by the evening of the same day. Heavier sessions can stretch symptoms toward the 48-hour end. Because the contributing processes overlap and clear at different rates, you may feel one symptom (say, fatigue) after another (say, headache) has faded.

Where DHM fits in the picture

If you’ve read about hangover supplements, you’ve likely seen dihydromyricetin (DHM), a flavonoid from the Oriental raisin tree (Hovenia dulcis). Most of the published DHM work involves animal models; a frequently cited example is a 2012 UCLA study in the Journal of Neuroscience that examined DHM’s interaction with GABA-A receptors in rodents. Human evidence is limited, and we won’t pretend otherwise. If you want the unhedged version of what the science does and doesn’t establish, start with what is DHM and when to take DHM. For how the next morning specifically tends to unfold, see the morning recovery stack.

Frequently Asked Questions

When does a hangover usually start? Symptoms generally appear as blood alcohol falls toward zero — often several hours after your last drink, which is why many people wake up with a hangover rather than feeling it while drinking.

When do hangover symptoms peak? For many people the worst symptoms land mid-morning to early afternoon — roughly 8–14 hours after the first drink, often after blood alcohol has already returned to zero. Timing varies with how much and how fast you drank.

How long does a hangover last? Most resolve within about 24 hours; heavier sessions can run toward 48. Because the contributing processes clear at different rates, individual symptoms may fade at different times.

Why do I get anxious the morning after drinking? Researchers associate morning-after anxiety with a rebound in GABA-A receptor activity as alcohol clears, sometimes alongside elevated stress hormones. We cover this in more detail in GABA rebound and alcohol anxiety.

Does sleeping it off help? Sleep is part of normal recovery, but alcohol disrupts sleep quality — particularly REM — so post-drinking sleep is often less restorative than usual. Recovery still largely comes down to time, food, and fluids.

Reviewed for accuracy against the cited primary literature. Hovenia is a liver-health supplement company; our product supports healthy liver function and is not intended to diagnose, treat, cure, or prevent any disease. This statement has not been evaluated by the FDA or Health Canada.

The brand behind this: Hovenia is single-ingredient pure DHM — 1,000 mg per serving, $1/serving, for the nights you drink. Join the waitlist → · See the product →