The 7 Stages and Symptoms of Alcohol Intoxication

Most of the serious cases I see did not start as emergencies in anyone’s mind. Someone drank heavily, fell asleep, and the people around them assumed they were just sleeping it off. By the time I met them, they had aspirated vomit or their breathing had dropped to eight breaths a minute. The seven-stage framework matters because it gives bystanders a language to describe what they are seeing and a threshold for when to act.

What Is Alcohol Intoxication?

Alcohol intoxication is the clinical state that results when ethanol enters the bloodstream faster than the liver can clear it. Your liver processes roughly one standard drink per hour using an enzyme called alcohol dehydrogenase (ADH). When you drink faster than that, BAC rises. Everything that follows, the loosened inhibitions, the slurred speech, the vomiting, the coma, is a direct consequence of rising BAC affecting the central nervous system.

Ethanol is a CNS depressant. It works primarily by enhancing GABA-A receptor activity (GABA is your brain’s main inhibitory signal) and suppressing glutamate activity (the main excitatory signal). The result is dose-dependent brain suppression. A little suppression feels relaxing. A lot of it stops your breathing.

The formal diagnosis, coded as ICD-11 6C40.0, requires a clinically significant alteration in consciousness, cognition, perception, or behaviour following alcohol consumption. In practice, a BAC reading plus clinical presentation is enough to stage it accurately.

How Blood Alcohol Concentration Is Measured

BAC is expressed as a percentage of alcohol per volume of blood. In most countries, the legal driving limit sits between 0.05% and 0.08%. Clinical impairment begins well below the legal limit.

These ranges overlap because body weight, sex, tolerance, food intake, and genetic variants in ADH and ALDH2 all shift where a person lands at a given BAC. A petite woman who rarely drinks may reach the confusion stage at 0.15%. A long-term heavy drinker may appear relatively functional at the same level due to CNS adaptation.

The 7 Stages of Alcohol Intoxication

Stage 1 — Subclinical (BAC 0.01 – 0.05%)

At this stage, most people feel nothing obvious or describe a slight warmth and ease. Behaviour looks normal to an outside observer. Underneath that surface, reaction time is already measurably slower and visual tracking is impaired. This is why driving after one or two drinks is genuinely dangerous even when you feel fine. Tests of psychomotor performance show deficits at BAC levels people would describe as sober.

Stage 2 — Euphoria (BAC 0.03 – 0.12%)

This is the stage most social drinking targets. GABA-A enhancement reduces social anxiety. Dopamine release in the nucleus accumbens creates the sense of reward that makes drinking feel good. Confidence rises. Inhibitions drop. Memory and attention start to slip, though most people at this stage would argue they are completely fine. They are not fine, but they are not in danger.

Stage 3 — Excitement (BAC 0.09 – 0.25%)

Emotion regulation breaks down here. Mood swings become more pronounced. Coordination is visibly impaired. Speech starts to slur because the cerebellum, the brain structure that coordinates fine motor movements, is significantly suppressed. Reaction time is roughly doubled. Judgement is substantially impaired. This is the range where most alcohol-related accidents, assaults, and risky sexual decisions occur. Someone at 0.15% is not equipped to assess their own level of impairment accurately.

Stage 4 — Confusion (BAC 0.18 – 0.30%)

Confusion in the clinical sense means genuine disorientation. The person may not know where they are or what time it is. Emotional lability is pronounced: laughing and crying within seconds of each other. Nausea and vomiting are common at this range. The vomiting reflex is still largely intact, which provides some protection, but it is also here that aspiration risk begins. If someone at this stage lies on their back and vomits, they can inhale the vomit into their lungs. Nystagmus (involuntary eye movements) is often visible.

Stage 5 — Stupor (BAC 0.25 – 0.40%)

The person is barely responsive. They may be awake in a technical sense but cannot stand, speak coherently, or respond meaningfully to questions. Gag reflex begins to diminish. This is the point where “sleeping it off” becomes genuinely life-threatening. The brain’s control over basic functions, breathing rate, heart rate, temperature regulation, is being suppressed. Hypothermia is a real risk if the person is in a cool environment.

At 0.30%, most people with no significant tolerance are unresponsive to pain. If you cannot wake someone up and they are at this stage, this is a medical emergency.

Stage 6 — Coma (BAC 0.35 – 0.50%)

True alcohol-induced coma. Breathing is suppressed. The protective airway reflexes are largely gone. Without medical intervention, hypoxia (dangerously low oxygen levels) begins damaging the brain. Aspiration pneumonia, cardiovascular collapse, and severe hypoglycaemia are all active risks. In a hospital, management at this stage includes airway protection (sometimes intubation), IV fluids, glucose monitoring, and thiamine supplementation to prevent Wernicke’s encephalopathy (a form of acute brain damage caused by vitamin B1 deficiency that alcohol depletes).

Stage 7 — Death (BAC Above 0.45%)

Respiratory depression becomes complete. The brainstem loses control of breathing. Cardiac arrhythmia can occur. Without resuscitation, death follows. The lethal BAC varies by individual. People with high tolerance may survive BAC levels that would kill a non-drinker, but no level of tolerance fully protects the brainstem at extreme concentrations. The LD50 (the dose lethal to 50% of the population) for ethanol is estimated around 0.45%, though deaths have occurred at lower levels, particularly when combined with other CNS depressants.

Factors That Change Where You Land on the Staging Scale

BAC does not tell the whole story. Two people at 0.20% can look completely different, and here is why.

Tolerance develops through two mechanisms. Metabolic tolerance means the liver upregulates CYP2E1, an enzyme that gives it a second pathway to clear alcohol. Pharmacodynamic tolerance means the brain’s GABA-A receptors become less responsive to ethanol. Both processes mean a chronic heavy drinker can appear functional at BAC levels that would render a casual drinker unconscious.

Sex matters significantly. Women have lower body water content and generally lower levels of gastric ADH than men, meaning alcohol reaches the bloodstream at higher concentrations relative to the same drink volume. A woman drinking the same amount as a man of equal weight will typically reach a higher peak BAC.

Genetics plays a substantial role. The ALDH22 variant, common in East Asian populations, slows the breakdown of acetaldehyde (the toxic intermediate produced when ADH metabolises alcohol). This causes the alcohol flush reaction: rapid flushing, nausea, and palpitations even at low BAC. It is also associated with a higher risk of alcohol-related cancers.

Food slows gastric emptying. Drinking on an empty stomach accelerates the rise in BAC. This is one reason the same number of drinks at a dinner feels very different from the same number on an empty stomach at a bar.

Polydrug use changes the picture entirely. Alcohol combined with benzodiazepines, opioids, or other CNS depressants is dramatically more dangerous than either substance alone. Both classes of drugs suppress the brainstem through overlapping mechanisms, and the combination can produce fatal respiratory depression at BAC levels that would not be immediately life-threatening on their own. Understanding how alcohol interacts with other substances is critical for anyone managing or witnessing intoxication.

Recognising Alcohol Poisoning vs. Being Very Drunk

The practical question bystanders face is: is this person dangerously intoxicated or just very drunk? The clinical signs to watch for are confusion that goes beyond drunkenness, skin that is cold, clammy, or bluish (cyanosis indicating oxygen deprivation), breathing that is slow or irregular (fewer than 10 breaths per minute), inability to be woken, and seizures. Any single one of these signs warrants calling emergency services.

What Happens in the Body During Alcohol Intoxication

Once alcohol is absorbed through the stomach and small intestine, it reaches the liver via the portal vein. ADH converts ethanol to acetaldehyde. ALDH2 then converts acetaldehyde to acetate, which is eventually broken down to water and carbon dioxide. When drinking outpaces this system, ethanol spills into systemic circulation. A secondary metabolic pathway through CYP2E1 activates at higher BAC levels, but this pathway generates reactive oxygen species (free radicals) that contribute to liver cell damage.

In the brain, the primary effect is GABA-A receptor potentiation and NMDA glutamate receptor inhibition. At low doses this produces disinhibition. At high doses it produces sedation, amnesia (blackouts occur because the hippocampus cannot form new memories at high BAC), and ultimately respiratory depression. You can read more about how alcohol is processed at a biochemical level in this explanation of alcohol metabolism.

The kidneys are also affected. Alcohol suppresses antidiuretic hormone (ADH, a different molecule from the enzyme alcohol dehydrogenase), causing increased urination. This is why alcohol is dehydrating, and why blood electrolyte imbalances including low sodium and low magnesium are common in people presenting with severe intoxication.

Alcohol Intoxication in People with Alcohol Use Disorder

Chronic heavy drinkers present differently. Tolerance can be so pronounced that a person with severe alcohol use disorder (AUD) shows only mild signs of intoxication at BAC levels that would incapacitate a non-drinker. The staging model above applies most accurately to people without established tolerance.

There is another clinical complication. In someone with AUD, apparent sobriety may actually represent early withdrawal, not genuine absence of intoxication. Alcohol withdrawal is driven by glutamate rebound, the same NMDA receptors that alcohol suppresses become hyperactive when alcohol is removed. This is why alcohol withdrawal can be medically dangerous and in some cases fatal. If someone with heavy regular drinking is trembling, sweating, or showing confusion despite a low or zero BAC, they may be in withdrawal, not simply recovering from intoxication.

The pattern I see most often is not dramatic. It is the person who drinks to a level they cannot fully account for the next morning, who has found their tolerance has shifted significantly over months, and who notices that what used to feel like Stage 2 now feels like Stage 1. That shift in tolerance is the body adapting to chronic exposure, and it is one of the diagnostic criteria for alcohol use disorder under the DSM-5. AUD is diagnosed on a spectrum from mild (2-3 criteria) to severe (6 or more criteria), and tolerance is just one of eleven clinical criteria. Loss of control over quantity, continued use despite harm, and craving are others.

If the pattern of intoxication you have been reading about is recognisable, whether in yourself or someone you care about, Phuket Island Rehab offers structured residential assessment and treatment in a medically supervised environment. Our approach addresses both the physical dependence and the psychological drivers that make stopping difficult without support.

Alcohol intoxication progresses through seven distinct stages tied to rising BAC, from subclinical impairment at 0.02% through to fatal respiratory depression above 0.45%. The mechanism throughout is CNS depression via GABA-A potentiation and NMDA inhibition, with the brainstem controlling breathing being the last structure to go and the most critical. Most deaths and serious harms occur not at the extreme stages but at Stages 4 and 5, where aspiration, hypothermia, and abandonment are the real killers. Tolerance, sex, genetics (particularly ALDH2 variants), food intake, and polydrug use all shift where any individual lands on that scale relative to their BAC reading.

Practically, the most important things to retain are the emergency signs that distinguish severe intoxication from alcohol poisoning: unresponsiveness to voice, breathing below 10 per minute, cyanosis, cold clammy skin, and seizures. Placing an unresponsive person in the recovery position, calling emergency services early, and not leaving them alone are the three actions that save lives. If you are recognising a pattern of intoxication that has become harder to control over time, that recognition matters and it is worth acting on.

As John A. Smith of Phuket Island Rehab puts it: “I have never had a family member tell me they called the ambulance too early. I have had plenty tell me they waited too long. When someone is at Stage 5 and you are not sure, make the call.”

What BAC level is considered alcohol poisoning?

Alcohol poisoning is generally considered to begin at BAC 0.25% and becomes life-threatening above 0.35%. At 0.25%, the gag reflex starts to diminish and the person is at serious risk of aspiration. Above 0.35%, respiratory depression is severe and without medical intervention, coma and death are real outcomes. In practice, anyone who cannot be roused and has been drinking heavily should be treated as a potential poisoning case regardless of estimated BAC.

How long does alcohol intoxication last?

The liver clears roughly 0.015% BAC per hour, regardless of what you do. There is no method that meaningfully accelerates this, coffee, food, water, and fresh air do not lower BAC. Someone who reaches 0.15% will take approximately 10 hours to return to zero. The duration varies based on body weight, sex, metabolic rate, and whether the liver is already compromised.

What are the first signs of alcohol intoxication?

The first signs are subtle: slight flushing of the face, a small increase in heart rate, and a sense of warmth and relaxation, all appearing at BAC around 0.02 to 0.05%. Reaction time is measurably slowed before any obvious outward signs appear. Most people at this stage would confidently report feeling fine, which is precisely why early intoxication is dangerous behind the wheel.

Can someone die in their sleep from alcohol intoxication?

Yes, and it happens more often than most people realise. BAC continues to rise after drinking stops because alcohol already in the stomach is still being absorbed. Someone who passes out at 0.20% can wake up at 0.30% or higher as absorption continues during sleep. If that person is on their back and vomits, aspiration is the immediate risk. If BAC climbs into the 0.35% range, respiratory depression during sleep is fatal without intervention.

How does alcohol tolerance affect intoxication stages?

Tolerance shifts the clinical presentation significantly but does not protect the body at the biological level. A person with high pharmacodynamic tolerance may appear to be at Stage 2 while their BAC is at Stage 4. The brainstem and cardiovascular system are still being suppressed at the same BAC, even if outward behaviour looks more controlled. This is one reason chronic drinkers can die at BAC levels that might appear manageable based on their behaviour. You can read more about how tolerance develops and what it means clinically in our guide to alcohol tolerance.

What should I do if someone is showing signs of alcohol poisoning?

Call emergency services immediately. While you wait: place the person on their side in the recovery position with their top knee bent forward to prevent them rolling onto their back. Never give them coffee, food, or water to “sober up.” Do not leave them alone for any reason. Stay on the line with the emergency dispatcher and monitor their breathing. If they stop breathing and you are trained in CPR, begin it.

Is alcohol intoxication the same as alcohol use disorder?

No. Acute alcohol intoxication is a single episode of CNS depression caused by drinking. Alcohol use disorder (AUD) is a chronic, relapsing medical condition defined by a cluster of behavioural and physiological criteria under DSM-5, of which repeated intoxication may be one element. Someone can become intoxicated without having AUD. However, frequent intoxication, particularly when it involves loss of control over how much was consumed, is one of the diagnostic signals worth taking seriously.