What Would My BAC Be?
If you are a driver who will not say no to alcohol prior to driving, BC's new Immediate Roadside Prohibition (IRP) makes it critical to understand how drinking affects your blood alcohol concentration (BAC). How many standard drinks, 12 ounces of beer, 5 ounces of wine or 1.5 ounces of hard liquor, can you consume and still not be over the 50 mg% (.05) level? More importantly, if you continue to imbibe, will your BAC rise, fall or stay the same?
I am a 180 pound (82 kg) male with no health issues that affect my ability to metabolize alcohol. If I consume 3 drinks in an hour, my peak BAC will be 50 mg%. The peak will occur about 40 minutes after I stop drinking although this may be affected by the consumption of food which can extend the absorption period. I have to limit myself to 2 drinks in the first hour to avoid passing the limit and build in a bit of a safety factor.
My body will eliminate about 15 mg% (.015) from my BAC each hour. This means that I can keep my BAC at the level of 2 drinks by drinking a bit more than one drink each hour after the first hour. Drink more than that and it will rise, less and it will fall.
Not all of us are 180 pound males, so let's take a look at a 120 pound female and a glass of wine. This will produce a BAC of 27 mg% (.027) in her, so she had better consider stopping there. She must also consume less than one more glass of wine each hour after that to remain at this level.
Given that there is some variability in everyone's ability to absorb and eliminate alcohol and doing these calculations can be problematic, it would probably be wise to stop at one or two at most depending on your size and sex. Otherwise, it's time for a taxi, designated driver, transit or shoe leather!