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When blood / breath alcohol levels are taken to determine how intoxicated a person is, does it depend on their tolerance ?

i.e. If you had two people of identical age, weight, fitness, etc.

person A, a non drinker, drank 1 measure of alcohol over a period and felt quite "drunk"

while person B, a frequent drinker drank the same measure of alcohol over the same period, but because of their built up tolerance felt and acted considerably more sober.

would they give the same blood, or breath alcohol readings, despite the effects on the person being different ?


Sorry if this is a very poorly formatted question from a chemistry point of view, i know absolutely nothing, nor have interacted with any of the sciences since school.

I was also not sure whether this comes under chemistry or biology, if it needs changing to the biology stack exchange site please advise

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Typical roadside 'breath-testing' measures metabolites produced in the metabolism of alcohol (primarily, they measure ethanal, oxidised ethanol). The level measured level of intoxication therefore definitely differs from person to person, and even day-to-day for everyone. Some people have higher metabolic rates, and will metabolise the alochol faster. Some people have greater amounts of alcohol dehydrogenase (enzyme that breaks down alcohol) than others. It follows, that a larger person will likely be able to consume more alcohol compared to a smaller person (compare the concentration of 1 g of salt in a small glass, compared to a large glass)

However, there isn't really any fudge room for arguing against the tests. And most police-forces will back up breath testing with far more rigorous blood tests.

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