Blood Alcohol Concentration (BAC)

Nov 9, 2017 | Alcohol, Blood Alcohol Content (BAC), Drink and Drive, DUI, Impaired Driving

What is Blood Alcohol Concentration (BAC)?


Blood Alcohol Concentration (BAC) is a measure of the amount of alcohol that is present in blood, based on the volume of alcohol consumed over a given period of time. Alcohol is metabolized by the liver, where enzymes break down the alcohol. In general, the liver can process one ounce of liquor (or one standard drink) in one hour. If you consume more than this, your system becomes saturated, and the additional alcohol will accumulate in the blood and body tissues until it can be metabolized. This is why having a lot of shots or playing drinking games can result in high blood alcohol concentrations that last for several hours.

Factors that affect your BAC:

The blood alcohol concentration can be measured within 30 to 70 minutes of consumption. Approximately one-half ounce of alcohol can be found in one shot of distilled spirits, one 12-ounce beer or one 5-ounce glass of wine. Different factors affect the body’s absorption of the alcohol:

Age – As you age, the intoxicating effects of alcohol become increasingly pronounced.

Gender – Alcohol is highly water soluble. Because women generally have lower water content in their bodies than men, they usually reach a higher BAC if they consume alcohol at a similar rate to their male counterparts, even if they are the same age and weight. Women also have a lower quantity of an enzyme in their stomachs that breaks down alcohol than men.

Rate of Consumption – The faster you consume alcohol, the faster your BAC will rise.  It takes around 20 to 40 minutes after a drink has been consumed for all the alcohol to be absorbed by the body.

Drink Strength – The higher percentage alcohol a drink contains, the more will end up in your bloodstream.

Body Type – The more you weigh, the more water you tend have in your body, which has a diluting effect on the alcohol you consume. That’s why larger people usually require more drinks to “keep pace” with their smaller companions.

Fat/Muscle Content – Fatty tissue is low in water content and cannot absorb alcohol, and the alcohol must remain in the bloodstream until the liver can break it down. However, tissues that are higher in water content, such as muscle, do absorb alcohol. Hence BAC will usually be higher in the person with more body fat.

Metabolism – “Metabolic tolerance” varies from person to person and describes the rate at which alcohol is processed by the body.

Emotional State – Stress can cause your body to divert blood from your stomach and small intestines to your muscles, and slow down the rate of absorption of alcohol into your bloodstream. When you calm down and your blood flows normally again, you may experience a surge in your BAC.

Medications – Many medications react negatively with alcohol, including cold or allergy pills and prescription drugs. They can intensify the effects of alcohol and even endanger your health. If you are taking meds, check the product labels for alcohol warnings, or consult your doctor or pharmacist before you drink.

Food – If you drink alcohol on an empty stomach, your BAC will be higher than a person who has eaten before drinking. Food slows the absorption in your bloodstream by keeping the alcohol you consume in your stomach and for a longer period of time.

Carbonation – Carbonated drinks such as sparkling wine or champagne, or mixed drinks with sodas may increase the rate at which alcohol passes through your stomach and result in a higher BAC.

Diabetes – Alcohol can affect the glucose levels of people who have diabetes and cause hypoglycemia. Diabetics should consult their doctors about drinking alcohol and avoid drinking on an empty stomach.

Alcohol Intolerance – Alcohol may cause adverse reactions in some, including flushing of the skin, nasal congestion, elevated heart rate, and reduced blood pressure.

Don’t Drink and Drive!

Everyday, 28 people in the US die from motor vehicle crashes that’s alcohol related (1 death every 51 minutes). Research have shown that behaviors such as steering and braking will be affected with BAC starting at 0.05. If you are interested, we have an article on the effects of alcohol on driving at different BAC levels.

Remember, a driver needs to multi-task by scanning the road, adjusting their speed and reacting to other vehicles and pedestrians. If a driver is impaired by alcohol, he/she will have trouble doing basic tasks to drive a car safely. So don’t drink and drive! If you must drink, get a designated driver or wait until you are sober before you hit the road.

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