How Alcohol Moves Through Your Body — and Why Only Time Sobers You Up
Coffee does not work. Neither does a cold shower, a big meal afterwards, or a run. Here is what actually happens to alcohol after you drink it, and why the timeline is so much longer than most people assume.
First, the one thing that matters
If you have been drinking, do not drive. No calculator, this site's included, can tell you whether you are fit to. Published equations carry wide variation between people and within the same person on different days, none of them models absorption in real time, and impairment of the exact skills driving requires begins well below every legal threshold in the world.
What the rest of this article can do is explain the shape of what happens — which turns out to be genuinely useful, because almost everything people believe about sobering up is wrong.
Where alcohol goes
Alcohol is a small, water-soluble molecule. It needs no digestion: around 20% is absorbed directly through the stomach wall and the rest through the small intestine, which is why the effect arrives within minutes rather than hours.
Once in the bloodstream it distributes into total body water — not into fat, and not simply in proportion to weight. This is why two people of identical weight can reach very different concentrations from the same drinks. Body composition, not body mass, sets the volume the alcohol has to spread through.
It is also why the Blood Alcohol Calculator asks for height and age as well as weight: it estimates your total body water rather than applying a single constant per sex, which is a meaningfully better approximation.
Why elimination is a straight line
Roughly 90% of the alcohol you drink is broken down in the liver, principally by alcohol dehydrogenase converting it to acetaldehyde, which is then converted to acetate. The rest leaves through breath, sweat and urine.
The important property is that this enzyme system saturates at very low concentrations. It is running flat out almost from the first drink, so it clears a fixed amount per hour rather than a fixed percentage. Pharmacologists call this zero-order elimination, and it is why a blood alcohol curve comes down as a straight line rather than tapering off.
The practical rate is about 0.015 percentage points an hour, with published variation between roughly 0.012 and 0.020. More alcohol does not make the liver work faster. It simply takes longer.
The things that do not work
Every folk remedy for sobering up shares a flaw: it changes how awake or how comfortable someone feels without changing how much alcohol is in their blood. That gap is precisely what makes them dangerous.
- Coffee. Caffeine can make an intoxicated person alert, and alert-but-impaired is arguably a worse state than obviously drunk — it restores the confidence to attempt things without restoring the ability.
- Food afterwards. Eating before or during drinking slows absorption, which lowers and delays the peak. Eaten after the alcohol has been absorbed, it does essentially nothing.
- Exercise and sweating. Only 5–10% of alcohol leaves through breath, sweat and urine, and that share does not rise meaningfully with activity.
- Cold showers and fresh air. Alertness, not concentration.
- Vomiting. Removes what is still in the stomach, not what has already reached the bloodstream.
The morning-after problem
This is where the linear elimination rate produces a result most people find surprising. Consider someone who reaches a peak of 0.16% — a heavy but not extraordinary night. At 0.015 percentage points an hour, returning to zero takes over ten hours.
Stop drinking at 2 a.m. and there can still be measurable alcohol at breakfast. Drink-driving offences the following morning are common for exactly this reason, and sleep does not accelerate the process — the liver works at the same rate whether you are awake or not.
The rule of thumb worth internalising is roughly one hour per standard drink once absorption is complete, and that is a floor rather than a promise.
Counting drinks is where most estimates go wrong
A US standard drink is 14 grams of pure alcohol: a 12 oz beer at 5%, a 5 oz glass of wine at 12%, or a 1.5 oz shot of spirits at 40%. A UK unit is 8 grams, which is a different quantity entirely.
The failure mode is counting containers rather than standard drinks. A 16 oz can of craft beer at 8% is closer to three standard drinks than one. A generous home pour of wine is often two. A cocktail with two spirits in it is two.
Nutritionally, alcohol also supplies 7 calories per gram — closer to fat than to carbohydrate — which the Calorie Calculator does not account for unless you add it yourself.
Why the same drinks affect people so differently
Two people of identical weight can finish the same three drinks and land at meaningfully different concentrations, and the reasons are worth knowing because none of them is willpower.
The largest factor is body water. Alcohol dissolves in water and not in fat, so the volume it spreads through is total body water rather than total body mass. Two 70 kg adults with different body composition have different volumes of distribution, and the one with more body water reaches a lower concentration from the same dose. This is also most of the reason women typically reach higher concentrations than men at the same weight — a difference in average body composition rather than anything about the liver.
Elimination rate varies too, by roughly a third between the slowest and fastest metabolisers, and it is not fixed within a person either: it drifts with liver health, with recent food, and with regular heavy drinking, which upregulates a second metabolic pathway and speeds clearance somewhat.
Then there is tolerance, which is the most dangerous variable because it changes how impaired you feel without changing how impaired you are. A regular drinker at 0.10% may appear composed and will still fail every objective test of reaction time and divided attention. Feeling fine is not evidence.
- Medication. Many common drugs interact with alcohol, and some — including certain antihistamines and sedatives — compound impairment substantially.
- Age. Total body water falls with age, so the same drinks produce higher concentrations later in life.
- Carbonation. Fizzy mixers speed gastric emptying slightly, which raises the peak.
- Speed. Four drinks over an hour and four over four hours produce very different peaks, because elimination is running the whole time.
Hangovers, dehydration and what helps
Alcohol suppresses vasopressin, the hormone that tells the kidneys to retain water, which is why drinking produces disproportionate urine output and next-morning dehydration. Rehydrating genuinely helps the headache and the malaise.
It does not, however, speed up elimination or shorten intoxication. Hangover severity correlates only loosely with blood alcohol anyway — acetaldehyde accumulation, disrupted sleep architecture, inflammation and congeners in darker spirits all contribute.
The interventions with any real support are unexciting: drink less, drink more slowly, eat beforehand, alternate with water, and give yourself more time than you think you need.
Frequently asked questions
Not medical advice. This calculator is for general informational purposes only and is not a substitute for professional medical guidance. Always consult a qualified healthcare provider before making decisions about your health. Read the full medical disclaimer.
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