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How fast does BAC go down?

On Behalf of | Jan 5, 2024 | DUI/DWI

Your blood alcohol concentration (BAC) is just a measure of the amount of alcohol in your system at any given time. This can be measured in various ways, with breath tests being the most common. But alcohol can also be detected with tools like urine tests or blood tests.

When someone consumes alcohol, their BAC rises, depending on how much they drink, how fast they do so, how much they weigh, if they are a chronic drinker and many other such factors. Even gender can play a role, as BAC goes up faster for women. 

The legal limit for drivers is a BAC of 0.08%. It typically takes people a few drinks to get to this point, but there can be a bit of a difference from one individual to the next, depending on the factors noted above.

The average rate of decline

After the person stops drinking, their BAC will continue to rise for a little while, as their body processes that final drink, and then will begin to drop. When it does, it goes down at an average of 0.015% per hour.

As you can see, this is a very slow decline. People often think that they’ll be safe to drive if they just take a break from drinking for a half an hour or 45 minutes.

But if that person‘s BAC was at 0.9%, they might not even be under the legal limit after a half an hour. It would take them roughly six hours to get back down to a BAC of 0.0%. 

The body just does not process alcohol very quickly, and this leads to people making mistakes where they drive while they are still under the influence. If this happens to you and you’re facing criminal charges, make sure you know about all of your defense options.