Time is the main reason that your blood alcohol concentration goes down. After you consume alcohol, your body begins metabolizing it and removing it from your system. You gradually sober up as this process takes place.
But it is not a fast process, contrary to what some people believe. As a general rule, most people see their BAC go down by about 0.015% every hour. If you had a BAC of 0.03%, it would take about two hours to get back to zero. If your BAC was over the legal limit at 0.09%, it would take roughly six hours.
What issues can this create?
This often contributes to drunk driving charges. Someone may wait a half hour or 45 minutes after they stop drinking, believing that their BAC will drop enough for them to drive safely. But they may not realize how long they actually need to wait. For someone who has a highly elevated BAC level to begin with, they are simply not going to get back into the legal range very quickly.
A related issue is that people sometimes face impaired driving charges the following day. A college student may stay out late with friends and then sleep for a few hours before getting up for a morning class, for example. Since it is the next day, they assume it is safe to drive, but they still have not waited long enough for their BAC to return to zero.
Drunk driving defense
A drunk driving conviction could lead to a license suspension, fines, fees and jail time. Since it can have such a major impact on your life, it is crucial that you know what defense options you have.