University of Rochester

University Health Service (UHS)
Health Promotion Office

Tolerance and Beyond

Resulting from the prolonged or heavy use of a drug or drug family, alcohol tolerance refers to a progressive state where, over time, an individual drinker will need to consume progressively more alcohol to achieve the same "buzz". There are two main types of tolerance that result from prolonged or heavy use of alcohol. The first type of tolerance, "metabolic" tolerance, results when, in response to the increase in consumption of alcohol, the liver increases its production of the enzyme alcohol dehydrogenase. The increase in enzyme production leads to a faster metabolization of the alcohol, thus leading to a lower peak BAC and faster elimination process. The second type of tolerance is known as "function tolerance", and results when a person's sensitivity to alcohol's effects is lowered as a result of chronic use. However, it must be noted that while a person's sensitivity to alcohol's effects may be decreased, his/her BAC continues to rise.

One of the main medical concerns with regards to metabolic tolerance is that an increase in the production of alcohol dhydrogenase and its corresponding increase in liver activity harms the liver. However, liver damage is not the only concern. Tolerance, particularly upwards of 50%, is a major warning sign of alcohol dependence and can signal a serious concern. In addition, tolerance often leads to an increase in a person's total consumption of alcohol, which, in addition to the aforementioned liver strain, can lead to weight gain and malnutrition. While not entirely health related, an increase in total consumption typically corresponds to an increase in cost, thereby affecting your personal finances and social economics. For more information on tolerance and the warning signs of alcohol misuse/abuse, see Alcoholism.

Absorption Rate Factors

There are many factors that affect the absorption rate of alcohol. These factors may decrease or increase alcohol's and individual's natural absorption rate, and if correctly understand, can be used as an effective method of slowing down alcohol's effects on the body and brain.
*Note: Absorption rates vary by individual, and can not be used in place of good judgment and moderate drinking.

Food plays a crucial role in the absorption rate of alcohol. For a person who has not eaten, peak BAC (point of greatest intoxication) typically occurs between 0.5-2.0 hours. For a person who has eaten, that peak BAC will typically not occur until 1.0-6.0 hours. When food is ingested with alcohol the pyloric valve at the bottom of the stomach closes in order to keep the food inside the stomach for proper digestion. In turn, the pyloric valve prevents the alcohol from immediately entering the small intestine where it is most effectively absorbed. While certainly some alcohol will be absorbed by the stomach, the absorption will be slower and the effects of the alcohol less substantive. Studies have shown that while the type of food ingested (ie: carbohydrate, protein, fat) does not have a measurable effect on this process, the size of the meal, as well as the lapse in time between the ingestion of food and the ingestion of alcohol, do have a measurable effect. In general, a large meal and a short lapse in time will have the most significant effect on the absorption rate of alcohol.

Another related contributing factor is the digestion process itself. Unlike food, alcohol rapidly moves from the stomach and small intestine into the blood stream where it is processed by the liver. It takes approximately one hour for the liver to process the amount of alcohol in one standard drink. It is from this known fact that the recommendation of one drink per hour for up to four hours was derived, for this will enable you to maintain a safe, yet desirable BAC. (See How much do you really drink? for more information.)

Strength of Drink
The strength of a drink plays a crucial role in its rate of absorption. The highest absorption rate occurs when the alcohol content of the drink is between 10%-30%. When the alcohol content is less than 10% the gastrointestinal tract has little desire to quickly process the alcohol, therefore leading to a slower absorption rate. Despite popular belief, the same end result is true of drinks with an alcohol content higher than 30%. Drinks with a high concentration of alcohol tend to irritate the mucous membranes of the gastrointestinal tract, leading to an increase in the production of mucous which in turn slows down the absorption of the alcohol. (See the chart under How much do you really drink? for more information regarding the alcohol content of your favorite drink.)

Body Type
As discussed in Understanding BAC, Blood Alcohol Content (BAC) is typically expressed as a percentage that reflects the total amount of alcohol in one's system divided by the total amount of blood. As blood is essentially water, an individual's BAC is affected by his/her percentage of body fat, the higher percentage of which corresponds to a lower percentage of body water and therefore a higher BAC. As women tend to have a higher percentage of body fat than men, given equal consumption, an average woman will have a higher BAC than an average man and therefore will get "drunker" faster. For the same physiological reason, a very muscled individual will tend to have a lower BAC, given equal consumption, than a less muscled individual. Given equal consumption, a heavier/larger individual will have a lower BAC than a lighter/smaller individual because the heavier person will have a higher percentage of body water to balance out the same amount of alcohol.

Gender Differences

Although not entirely understood, studies have shown that women have more of the enzyme that breaks down alcohol, and therefore typically process alcohol up to ten times faster than men. Although this phenomena leads to a quicker elimination of alcohol, it also leads to a faster, higher BAC. It has also been shown that during the premenstrual phase a woman will achieve a higher BAC than she would after consuming an equal number of drinks during a different cyclical phase. The gender differences of most significance are related to body type. See Absorption Rate Factors and Body Type for more information.

The Effect of Expectations

Over the past few decades a series of studies were conducted to determine how much pre-established expectations affect an individual's drinking experience. Conclusively all studies demonstrated that an individual's pre-conceived level of drunkenness was achieved whether or not the individual consumed a corresponding quantity of alcohol. In other words, the people who set out to the bar to get drunk tended to "get drunk" even if they were given look-a-like drinks, and those who intended on staying sober tended to "stay sober" even if they were given drinks that contained more alcohol than they thought.

Clearly an individual's pre-conceived expectation of drunkenness does have a significant effect on his/her drinking experience. Furthermore, it is also clear that those who did not set out to get intoxicated were less likely to do so. Although you may in fact desire to get drunk, try to avoid drinking solely for that purpose. Make the focus of your evening something other than alcohol, ex: your friends, the music, the party, the hot guy/girl across the room. Make alcohol the sideshow, and think sober.

Other Influencing Factors

Other Drugs/Medications
Although traditionally consumed in liquid form, alcohol is no less of a drug than aspirin, Sudafed, or cocaine. Like all drugs, alcohol can react with other drugs in unpredictable and sometimes deadly ways, and can cause extensive internal damage to the lining of the stomach, esophagus, and liver. For example, when mixed with alcohol, acetaminophen (Tylenol ®) can significantly increase one's chance of liver damage. Furthermore, other depressant drugs (ie: certain pain killers, sleeping pills, cold medicine, etc.) can multiply the effects of alcohol up to ten times. For all of the above reasons and more, avoid mixing alcohol with any other drug or medication, prescription or otherwise, without first consulting a licensed physician.

General fatigue or tiredness will lead to a higher BAC than normal as one's liver is less efficient at processing and/or eliminating alcohol when one's general energy level is low. Furthermore, as alcohol is a depressant, consuming alcohol when tired will, in general, simply increase one's level of tiredness while magnifying alcohol's traditional effects.

The main concern with regards to illness and alcohol consumption is that whether an individual is currently sick or just getting over an illness, inevitably s/he will be dehydrated. As discussed in Absorption Rate Factors and Body Type, a lower percentage of body water will lead to a higher BAC. In addition, one who is ill or recently recovered is more likely to suffer from mild fatigue than a healthy individual, and may still be taking (or have residual effects) of various medications. Bottom line - avoid ingesting alcohol when sick or recovering. Give your body time to establish a healthy equilibrium before bombarding it with alcohol.

For more information, contact Linda Dudman in the UHS Health Promotion Office at (585) 273-5770 or

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Last modified: Thursday, 10-Apr-2014 16:32:12 EDT