How Alcohol Effects Us: The Biphasic Curve

by David J. Hanson, Ph. D.

Most people think that if a few drinks make them feel good then a lot of drinks will make them feel even better. But that’s not true. Although a few drinks will make them feel better, more will make them feel worse. It’s called the biphasic (or two part) effect.

Here’s what happens. People tend to feel better as their blood alcohol concentration (BAC) rises to about .05 (.055 to be exact). That’s the first phase or part. If people drink more and their BAC rises above .055, the negative effects of drinking increase and hangovers become worse. That’s the second phase. So it’s clearly smart to stop during the first phase and not progress into the second phase.

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How much does it take to reach a BAC of about .05? The following charts provide guidelines. Remember that blood alcohol level is affected by gender, speed of drinking, type and amount of food consumed, and some medications.

MALE BLOOD ALCOHOL CONCENTRATION GUIDE 2
Number of
Drinks Per Hour
Body Weight in Pounds  
110 120 140 160 180 200 220 240
% of Alcohol in Bloodstream
1 .04 .03 .02 .02 .02 .02 .02 .02 Driving
Skills
Impaired
2 .08 .06 .05 .05 .04 .04 .03 .03
3 .11 .09 .08 .07 .06 .06 .05 .05
4 .15 .12 .11 .09 .08 .08 .07 .06
5 .19 .16 .13 .12 .11 .09 .09 .08 Legally Intoxicated in all States
6 .23 .19 .16 .14 .13 .11 .10 .09
7 .26 .22 .19 .16 .15 .13 .12 .11
8 .30 .25 .21 .19 .17 .15 .14 .13
9 .34 .28 .24 .21 .19 .17 .15 .14
10   .31 .27 .23 .21 .19 .17 .16
FEMALE BLOOD ALCOHOL CONCENTRATION GUIDE 2
Number of Drinks Per Hour Body Weight in Pounds  
100 120 140 160 180 200 220 240
% of Alcohol in Bloodstream
1 .05 .04 .03 .03 .03 .02 .02 .02 Driving
Skills
Impaired
2 .09 .08 .07 .06 .05 .05 .04 .04
3 .14 .11 .10 .09 .08 .07 .06 .06
4 .18 .15 .13 .11 .10 .09 .08 .08 Legally Intoxicated in all States
5 .23 .19 .16 .14 .13 .11 .10 .09
6 .27 .23 .19 .17 .15 .14 .12 .11
7 .32 .27 .23 .20 .18 .16 .14 .13
8 .36 .30 .26 .23 .20 .18 .17 .15
9 .41 .34 .29 .26 .23 .20 .19 .17
10 .45 .38 .32 .28 .25 .23 .21  

Here are some hints for maintaining a moderate blood alcohol concentration:

Drinking too much alcohol is never a good idea.

 

References and Readings

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