Alcohol intoxication is a temporary physical and mental impairment caused by drinking more alcohol than your body can process. It begins with subtle changes in mood and judgment at low levels and can progress to life-threatening suppression of breathing and heart rate at high levels. The average human body clears roughly one standard drink per hour, so intoxication builds whenever intake outpaces that rate.
How Alcohol Affects the Brain
When you drink, ethanol crosses into your bloodstream and reaches the brain within minutes. There, it amplifies the activity of GABA, the brain’s main calming neurotransmitter. GABA normally works by allowing charged particles called chloride ions to flow into nerve cells, making them less likely to fire. Ethanol boosts this effect in two ways: it acts directly on the receptors that respond to GABA, and it increases the amount of GABA released from nerve endings in the first place. The result is a widespread slowdown in brain signaling.
At the same time, alcohol suppresses glutamate, the brain’s primary excitatory neurotransmitter. With the “go” signals dampened and the “stop” signals amplified, the nervous system shifts toward sedation. This is why even small amounts of alcohol relax muscles, lower inhibitions, and slow reaction time. As drinking continues, these effects deepen, eventually reaching brain regions that control breathing, heart rate, and body temperature.
What Each Blood Alcohol Level Feels Like
Blood alcohol concentration (BAC) is the standard measure of intoxication, expressed as a percentage of alcohol in your blood. According to Cleveland Clinic, here is what happens at each stage:
- 0.02%: Slight mood change, mild relaxation, minor loss of judgment. Most people wouldn’t recognize they’re impaired.
- 0.05%: Lowered alertness, feeling uninhibited, noticeably impaired judgment.
- 0.08%: Reduced muscle coordination, difficulty detecting danger, impaired reasoning. This is the legal driving limit in all U.S. states.
- 0.10%: Slurred speech, slowed thinking, reduced reaction time.
- 0.15%: Nausea, vomiting, loss of balance, and significant loss of muscle control.
- 0.15% to 0.30%: Confusion, vomiting, drowsiness. Many people lose the ability to walk or stand.
- 0.30% to 0.40%: Loss of consciousness and a high likelihood of alcohol poisoning.
- Above 0.40%: Risk of coma and death from respiratory arrest.
These ranges are averages. Two people at the same BAC can feel very different depending on tolerance, body composition, and how quickly they drank.
When Intoxication Becomes Life-Threatening
Alcohol overdose happens when the concentration of alcohol in the blood climbs high enough to shut down the brain regions that keep you alive. The National Institute on Alcohol Abuse and Alcoholism identifies the warning signs: mental confusion, difficulty staying conscious, vomiting, seizures, trouble breathing, a slow heart rate, clammy skin, extremely low body temperature, and a dulled or absent gag reflex. That last detail matters because someone who vomits without a functioning gag reflex can choke to death.
One of the most dangerous features of severe intoxication is that BAC can keep rising even after a person stops drinking. Alcohol already in the stomach and intestines continues to absorb into the bloodstream. Someone who passes out with a rising BAC is in more danger than their current symptoms suggest.
How Your Body Processes Alcohol
Your liver does the heavy lifting. Enzymes break ethanol into acetaldehyde (a toxic compound responsible for many hangover symptoms), which is then converted into acetate and eventually cleared. For a person weighing about 70 kg (154 lbs), the liver handles roughly 7 grams of alcohol per hour. A standard drink in the United States contains 14 grams of pure alcohol, whether that’s 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of distilled spirits. So one drink takes approximately two hours to fully metabolize, not one hour as many people assume.
The rate isn’t perfectly constant. At higher concentrations, the liver’s enzymes become saturated and processing slows relative to the amount in your system. There is no way to speed this up. Coffee, cold showers, and food after drinking do not accelerate alcohol clearance. Only time works.
Why Women Are Affected More Quickly
Women generally reach higher BAC levels than men after consuming the same amount of alcohol, even when body weight is the same. Research published in PubMed found that the primary reason is a difference in first-pass metabolism, the process by which the stomach breaks down some alcohol before it ever reaches the bloodstream. Women have significantly less activity of a key stomach enzyme involved in this step, which means more alcohol passes intact into the blood.
The effect is more pronounced with stronger drinks. When researchers tested beverages at different alcohol concentrations, the gender gap in first-pass metabolism was larger with higher-concentration drinks (like spirits) than with dilute ones. Women also had 42% slower gastric emptying, meaning alcohol sat in the stomach longer but without the enzymatic activity needed to break it down efficiently. These combined pharmacokinetic differences increase vulnerability to both intoxication and long-term organ damage.
Factors That Change How Fast You Get Intoxicated
Body weight and composition play a major role. Alcohol is water-soluble, so people with more body water (generally those who are larger or have more muscle mass) dilute the same amount of alcohol across a larger volume, resulting in lower BAC. People with higher body fat percentages, regardless of total weight, tend to reach higher blood alcohol levels because fat tissue doesn’t absorb alcohol the way lean tissue does.
Drinking speed is the most controllable variable. Because the liver processes alcohol at a relatively fixed rate, consuming several drinks in a short window causes BAC to spike. Carbonated mixers can accelerate absorption in the small intestine, pushing alcohol into the bloodstream faster than still beverages. Medications that affect liver enzymes or central nervous system function, including many common prescriptions for anxiety, pain, and sleep, can dramatically intensify alcohol’s effects at any BAC level.
Tolerance, built through repeated drinking, changes how impaired you feel at a given BAC but does not change the BAC itself or the physical damage alcohol does to your organs. A person with high tolerance may appear functional at a BAC that would incapacitate someone else, but their liver, heart, and brain are experiencing the same toxic load.
How Long Intoxication Lasts
The math is straightforward but often underestimated. At an average clearance rate of about 7 grams per hour, four standard drinks (56 grams of alcohol) would take roughly eight hours to fully metabolize. BAC typically peaks 30 to 60 minutes after the last drink if you haven’t eaten recently, though food in the stomach can shift that window. Even after BAC returns to zero, cognitive and motor impairments can linger. Reaction time, fine motor coordination, and decision-making often remain measurably worse for hours after the alcohol itself has been cleared, which is why “sleeping it off” doesn’t always mean you’re safe to drive the next morning.
Hangovers are a separate but overlapping process, driven by dehydration, inflammation, and the toxic byproducts of alcohol metabolism. They typically peak 12 to 14 hours after BAC hits zero and resolve within 24 hours, though heavy drinking episodes can cause lingering fatigue and cognitive fog for up to 72 hours.