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Addiction and Substance Abuse

It is taking less alcohol to blackout




I noticed recently that it is taking less alcohol for me to forget things than it used to. Before it would take several drinks to blackout but now it only takes two. I drink often. Do you think that my brain is starting to show the damage of my drinking?

Thank you!


A blackout is the result of alcohol’s ability to interfere with the process of incorporating events experienced while under its influence into memories of those events. These periods of memory loss, which occur particularly when large amounts are consumed rapidly, can be of two types:

In clinical studies, the minimal blood alcohol level (BAC) necessary for a blackout to occur is in the 0.140–0.200 range. However, other studies have noted that at least as important as the actual measured BAC is the rate of rise of the BAC – in other words, how rapidly the blood alcohol level is on the increase.

Factors that can affect this include a person’s general health, whether one is dehydrated or ill, whether one drinks on an empty stomach, or drinks by gulping, among others.

Your question pertains to a change in the amount of alcohol needed to cause a blackout, in this case a lesser amount than previously noted. It is well known that as a younger person begins drinking more heavily, the amount required to cause drunkenness actually INCREASES, due to what is known as increased TOLERANCE. However, later on, usually after months or years of heavy drinking, the tolerance to alcohol’s effects may paradoxically DECREASE. This is caused by changes in the person’s liver function resulting in a decreased ability to metabolize alcohol (i.e., detoxifying the body of alcohol).

So, in this case, it appears that you may be experiencing decreased tolerance due to liver damage (rather than any brain damage), which causes you to blackout after a lesser number of drinks. It is also possible that those two drinks are being consumed more rapidly than before, thereby causing a rapid rise in BAC and a blackout as the result.

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Response by:

Bruce J Merkin, MD Bruce J Merkin, MD
Clinical Instructor of Psychiatry
School of Medicine
Case Western Reserve University