Over the limit

What we eat or drink can affect us in different ways at different times. It is hard to know how a certain amount of alcohol will affect you, even if it is the same amount you usually drink. A pint may hit you harder if you are tired, or if you drink it at lunchtime rather than after dinner. Your health and your mood also play a role in how alcohol affects the way you behave, what you see, and how quickly you react.

Even if they vary by degree, the effects of drinking almost always include your system slowing down – including the nerves that control your muscles. Regular drinkers often learn to hide some of the obvious signs of alcohol use. But while you can sometimes fool your friends and even yourself, you can't trick your body.

Far too often the newspaper reports that "The autopsy showed the driver had a blood alcohol concentration of .16, double the legal limit." Do you know what the number means?

As blood flows through the body, it releases alcohol into the lungs in proportion to its concentration in the blood. Police officers often use a breathalyzer to measure Blood Alcohol Concentration (BAC).

BAC refers to how much alcohol is in someone's blood. While under Canadian law, a driver is not over the legal limit until he or she has reached a BAC of more than 80 milligrams of alcohol per 100 millilitres of blood (commonly expressed as .08 mg or .08). You may be impaired at lower levels. Impaired means your ability to drive is significantly affected by drugs or alcohol.

As you drink, your BAC goes up. If you are caught driving impaired and/or over the legal limit, you will face many problems.

What is a “drink”?

Wine, beer and spirits each have different concentrations of alcohol. Most beers contain five per cent alcohol, while wines contain 11 to 12 per cent. Spirits, such as vodka or rye, contain 40 per cent or more.

As a rough guide, a 341mL (12 oz.) bottle of beer, a 148mL (5 oz.) glass of wine or a 44mL (1.5 oz.) shot of spirits usually contains the same amount of alcohol-about 13.5 grams. These amounts are often called "standard servings." However, it is easy to drink more than you realize.


  • If you are drinking draft beer rather than bottled beer, you may order a pint – which may be up to 50 per cent bigger than a standard serving.
  • You may drink half a bottle of wine by refilling a large glass twice. If you do, you have had two-and-a-half standard servings.
  • If you don't use a shot glass when making a mixed drink, you may drink more than you intend.
  • Alcohol concentrations vary among brands and types of drinks. For instance, some light beers contain less than 5 per cent alcohol, while others may contain more.

As you can see, defining "a drink" is not simple.

What happens to the alcohol?

No matter what size drink you have, your bloodstream will spread it throughout your whole body in 30 to 90 minutes.

The alcohol then moves to your liver, which breaks over 90 per cent of it down into carbon dioxide and water. The rest passes, unchanged, out of your body.

All of this takes about two hours for one standard serving. Any other alcohol you drink during that time will stay in your blood until your liver can deal with it, so your BAC rises quickly to a peak. If you stop drinking, your BAC will slowly start to drop-but it will most likely take much longer to fall than it did to rise.

You are special

Did you know that your body type affects how much blood you have? It is true. The lighter you are, the less blood you have. So if you weigh 68 kg (150 lb.) and you drink as much alcohol as someone of the same sex who weighs 80 kg (175 lb.), you will have a higher BAC.

It is also true that muscle tissue contains more blood while fatty tissue contains more water. So if you have a lot of body fat and you drink as much alcohol as someone of the same sex who is muscular, your BAC will be higher. Why? Because there is less blood for the alcohol to mix with, the ratio of alcohol to blood is higher.

Since women tend to be smaller than men and have more fatty tissue, a woman who drinks as much alcohol as a man usually has a higher BAC – often much higher.

Time is on your side

You may have heard that you can keep your BAC under the legal limit by drinking no more than one standard drink per hour. This rule only works for a couple of hours and mainly for men. A better plan is to have no more than two standard drinks in an evening.

Maybe you have heard that you can sober up faster by dancing, jogging, peeing, taking a shower or drinking water or black coffee. Don't believe it! The only thing that will really lower your BAC is time. If you are over the legal limit, it will take about six hours for your body to get rid of all the alcohol.

So, what's the bottom line? If you drink, don't drive.

Source: Excerpt from Transport Canada’s Smashed: A Sober Look at Drinking and Driving