Alcohol & Health
Treatment
Helping Alcoholics
Medically Reviewed by Dr P. E. Pancoast, MD
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Alcohol tolerance refers to the amount of alcohol someone can consume before feeling its effects.
Someone with a high tolerance requires more alcohol to feel its effects or appear intoxicated. Someone with a low tolerance requires less.
Signs of a high alcohol tolerance include:
Tolerance can encourage greater alcohol consumption which contributes to alcohol dependence and can cause adverse health effects.
Drinking more alcohol can increase tolerance. The human body can adapt to increased alcohol use, resulting in more rapid metabolism of alcohol.
A more rapid metabolism means those who drink alcohol regularly can seem less intoxicated than those who have consumed a similar amount in the same session.
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According to the National Institute on Alcohol Abuse and Alcoholism, functional tolerance is a lessened response to alcohol, that is independent of the rate of metabolism of alcohol. People develop functional tolerance when brain functions begin to adapt to compensate for its effects.
The five types of functional alcohol tolerance include:
Environment-dependent tolerance is an accelerated tolerance to alcohol when it is continually consumed in a familiar environment.
This type of tolerance is why some people can consume more alcohol with a lesser degree of intoxication in a familiar environment compared to a new environment.
Environment-independent tolerance is an accelerated tolerance to alcohol when it's continually consumed in a new environment or accompanied by different cues.
This type of tolerance is why some people feel fewer of alcohol's effects while in a new environment.
Metabolic tolerance is when the body flushes alcohol out of its system more rapidly.
Chronic heavy drinkers can eliminate alcohol two to four times as fast as moderate drinkers and therefore need double or greater amounts of alcohol to maintain the same blood alcohol concentration (BAC).
Learned tolerance is learned behavior that compensates for alcohol’s impairing effects.
Over time, people can develop the ability to control their motor skills better while under the influence of alcohol, giving the appearance of greater alcohol tolerance.
This can happen if you drink every night.
Acute alcohol tolerance develops during a single exposure to alcohol. It's when impairment is more significant at the beginning of a drinking session rather than the end, even if the BAC is the same at both times.
Acute alcohol tolerance can cause someone to drink more alcohol, wrongfully assuming they are less intoxicated than they are.
Genetic factors influence alcohol tolerance. For some people, low tolerance is caused by a natural lack of an enzyme called acetaldehyde dehydrogenase.
When most people ingest alcohol, an enzyme called alcohol dehydrogenase (LDH) helps metabolize the ethanol. The liver converts the ethanol into acetaldehyde, a substance that can cause cell damage. Another enzyme called aldehyde dehydrogenase 2 helps convert acetaldehyde to acetic acid, which is nontoxic.
In people with alcohol intolerance, a genetic mutation makes ALDH2 less active or inactive. As a result, the body can’t convert acetaldehyde to acetic acid. Acetaldehyde starts to build up in your blood and tissues, causing symptoms.
People of Asian and Native American descent are more likely to have this enzyme deficiency.
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Functional tolerance can lead to alcohol use disorder (AUD).
Because the drinker doesn't experience significant impairment due to drinking, functional tolerance may facilitate increasing amounts of alcohol, resulting in dependence and alcohol-related organ damage.
This can make heavy drinking and alcohol use disorder more likely, which can have various long-term health consequences.
These include:
Those with high tolerances for alcohol are also more at risk for binge drinking and overdoses.
Higher alcohol tolerance can give a false impression of how drunk someone is.
You may think a person who is not stumbling or slurring their words is less intoxicated. However, you shouldn't assume that those with a higher tolerance aren't impaired.
Tasks that require concentration will be just as hard for them as they are for people with lower tolerance. The amount of alcohol consumed still affects them even though it may not appear so, even to them.
If you think your tolerance is rising, you should temporarily stop drinking to give your body a break.
Most people can decrease their alcohol tolerance through abstinence.
Once you’ve lowered your tolerance, you won’t need as much alcohol to feel the effects, making it far easier to drink sensibly. If you’ve fallen into a heavier drinking pattern, having a break also allows you to build new, more positive drinking patterns.
If you suspect that you or someone you know may be addicted to alcohol, you should immediately seek medical treatment.
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