Alcohol poisoning is a systemic shutdown. When blood alcohol concentration (BAC) climbs above roughly 0.31%, the brain loses its ability to manage basic survival functions: breathing, heart rate, temperature regulation, and the reflexes that keep you from choking on your own vomit. At a BAC above 0.40%, coma and death from respiratory arrest become real possibilities. Here’s what’s happening inside the body at each level.
Your Brain Starts Shutting Down
Alcohol depresses brain function in a way that resembles an anesthetic. It does this through two mechanisms working simultaneously. First, it amplifies the activity of GABA, the brain’s primary “slow down” chemical, by triggering more of it to be released and by making brain cells more responsive to it. Second, it suppresses glutamate, the brain’s primary “speed up” chemical. The combined effect is like slamming the brakes and cutting the engine at the same time.
At lower BAC levels (0.16 to 0.30%), this produces confusion, difficulty walking and speaking, memory blackouts, and loss of consciousness. Push past 0.31% and the suppression reaches the brainstem, the part of the brain responsible for keeping you alive without conscious effort. That’s where breathing rhythm, heart rate, and protective reflexes like gagging and coughing are controlled. Once alcohol reaches those circuits, the body can no longer reliably perform the functions you never have to think about.
Breathing Slows or Stops
The most immediately dangerous effect of alcohol poisoning is respiratory depression. The brainstem normally monitors carbon dioxide levels in your blood and adjusts your breathing rate automatically. High concentrations of alcohol interfere with that feedback loop, causing breathing to become slow, irregular, or shallow. In severe cases, breathing stops entirely.
When breathing slows enough, oxygen levels in the blood drop and carbon dioxide builds up. This creates a condition called respiratory acidosis, where the blood becomes dangerously acidic. Respiratory arrest, along with severe acidosis, is one of the strongest predictors of death in alcohol poisoning cases. It’s also the single most common reason people with alcohol poisoning end up on a ventilator in the hospital.
The Gag Reflex Disappears
Alcohol’s sedating effect suppresses both the cough reflex and the gag reflex. This matters enormously because vomiting is common during alcohol poisoning, and without a functioning gag reflex, vomit can slide into the airway and lungs. This is called aspiration, and it can cause immediate suffocation or lead to a serious lung infection.
In one study of intubations performed on acutely intoxicated patients in emergency departments, about 16% of cases involved placing a breathing tube specifically to protect the airway from vomit or blood. This is why the common advice to “let them sleep it off” is dangerous for someone who may be poisoned rather than just drunk. A person lying on their back without a gag reflex can die quietly from inhaling vomit.
Your Heart Rhythm Changes
Alcohol at high levels directly disrupts the heart’s electrical system. A large study of intoxicated individuals found that cardiac arrhythmias occurred in nearly 31% of participants, with the most common being sinus tachycardia, a resting heart rate above 100 beats per minute. For every unit increase in breath alcohol concentration, the odds of an arrhythmia rose by 75%.
Beyond a rapid heartbeat, alcohol reduces the normal variation in heart rhythm that reflects healthy nervous system control. Other rhythm disturbances that can appear include premature heartbeats originating from both the upper and lower chambers of the heart, and atrial fibrillation, a chaotic rhythm in the upper chambers. In the most extreme cases, when body temperature drops low enough (more on that below), the heart can stop altogether.
Body Temperature Drops
Alcohol causes blood vessels near the skin’s surface to widen. This is why drinking makes your face flush and your skin feel warm. But that warmth is deceptive. You’re actually radiating core body heat outward through your skin at an accelerated rate, and as BAC rises, the brain’s temperature regulation center becomes increasingly impaired.
The result is hypothermia. During alcohol poisoning, body temperature can fall low enough to trigger cardiac arrest. The skin often becomes cold and clammy to the touch. Someone with alcohol poisoning may look pale or develop a bluish tint around the lips and fingertips, a sign that oxygen levels in the blood are dropping. This combination of low body temperature and poor oxygenation creates a reinforcing cycle: cold muscles demand less oxygen but also become less effective at shivering, which is the body’s primary way of generating emergency heat.
Blood Sugar Can Crash
Your liver is responsible for both processing alcohol and maintaining blood sugar levels between meals. It can’t do both well at the same time. When the liver is metabolizing alcohol, a chemical byproduct shifts the liver’s internal balance in a way that blocks gluconeogenesis, the process of manufacturing new glucose. This is especially dangerous for someone who hasn’t eaten recently or whose liver is already compromised.
In well-fed, healthy adults, the body has enough stored glucose (glycogen) to buffer this effect. But in someone who’s been drinking instead of eating, or who has been fasting, the drop in blood sugar can become severe. Hypoglycemia during alcohol poisoning can cause seizures, loss of consciousness, and brain damage. It also mimics and compounds the sedating effects of the alcohol itself, making it harder for bystanders or even medical professionals to assess how much danger the person is in.
What Happens at the Hospital
There’s no drug that reverses alcohol poisoning the way naloxone reverses an opioid overdose. Treatment is entirely supportive: keep the person alive and stable while their body processes the alcohol.
The most critical intervention is protecting the airway. If someone is unconscious with a depressed gag reflex, medical teams may place a breathing tube to prevent aspiration and ensure adequate oxygen delivery. About 9% of intubations in acutely intoxicated patients happen because non-invasive methods like oxygen masks can’t maintain adequate breathing on their own. Intravenous fluids help address dehydration and can deliver glucose if blood sugar is low. Body temperature is monitored and managed with warming measures if hypothermia is present. Heart rhythm is tracked continuously.
The liver processes alcohol at a roughly fixed rate, typically reducing BAC by about 0.015% per hour in most adults. At a BAC of 0.40%, that means roughly 24 hours or more before alcohol is fully cleared, during which time every system in the body remains under stress. The severity of metabolic acidosis at the time of hospital admission is one of the strongest predictors of whether someone survives. Early arrival matters enormously.
Why It Escalates So Quickly
One reason alcohol poisoning catches people off guard is that BAC continues to rise after someone stops drinking. Alcohol in the stomach and small intestine keeps absorbing into the bloodstream for 30 to 90 minutes after the last drink. Someone who seems “just really drunk” at the end of a night can cross into poisoning territory while apparently sleeping. The difference between a BAC of 0.25% and 0.40% is the difference between a blackout and a potentially fatal emergency, and the body gives few obvious external warnings as it crosses that line.
The signs that distinguish poisoning from heavy intoxication are subtle but important: breathing that’s very slow (fewer than eight breaths per minute) or irregular with long pauses, skin that’s cold or bluish, an inability to be woken up, and continuous vomiting while unconscious. These indicate that the brainstem is losing the fight to keep basic systems running.