Understanding how blood alcohol concentration levels effect you is critical to safety. If you’re planning on drinking alcohol you ought to understand what BAC is, and why this number can make the difference between staying a law abiding person and breaking the law, and even worse, BAC can mean the difference between living and dying!



BAC – What is it?

BAC is exactly what it sounds like – blood alcohol concentration. In layman’s terms, whenever one drinks alcohol based drinks, the alcohol is absorbed into the body. Obviously whenever you consume more, more alcohol is put in your blood stream, increasing your blood alcohol concentration. Numerically, this number is the parts of alcohol per total parts of blood. Practically, it’s a way of measuring inebriation. All over the United States, a person is lawfully drunk if or when their BAC level is greater than .08% when driving a motor vehicle or while in public.

Would you think it is a high or low figure? It might seem that only a tenth of one percent is a minuscule number. Unfortunately, a blood alcohol concentration of greater than .20 – a fifth of a single percent, can be lethal!

BAC level chart

How to calculate BAC:

One factor to recognize when examining blood alcohol concentration is body mass. Naturally, the heavier the individual, the more tissue mass and therefore blood, the more blood, the more the alcohol is diluted. So a large person may drink more than a lighter individual and still have the same BAC as the lighter person who is drinking less.

The 2nd factor, every bit as important as the first, is what alcohol is consumed. You might have been told that most traditional beverages have the same amount of alcohol in them (12 oz. Beer, 5 oz. Glass of wine, 1.5 oz – 1 shot of hard alcohol). Each one of these drinks has approximately .60 ounces of alcohol apiece. When you are drinking alcohol away from your home it is advised to cautiously observe your hard alcohol drinks because night clubs and dining establishments are famous for being “heavy handed.”

The 3rd and just as vital issue is time. Rationally, the more you consume in a shorter time period the greater your blood alcohol concentration will be.

How long does alcohol stay in your blood?

For those who didn’t know, alcohol is toxic to your body. Mercifully, for those who consume alcohol, the human body is great at getting rid of toxic compounds from the system and alcohol is not an exception.

Approximately 10% of the alcohol absorbed within your body is expelled by way of sweating, respiration and urine, the remainder has to be broken down internally. It is the purpose of the liver to detoxify the rest. The liver can remove approximately half an ounce of alcohol per hour – a tad less than a single ordinary drink. Don’t forget it takes as much as 40 minutes after the alcohol is actually consumed for it to become completely assimilated into your system. If the normal rate of elimination is .015% every hour, even at legal BAC level of.08%, it should take the human body in excess of five hours to remove all of it.

Obviously, if you have liver problems, or another impairment, lowering you blood alcohol concentration will take even longer. So, how long alcohol stays in your blood is a tricky question.

See Highway Safety Research Center for more on BAC

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