Blood Alcohol Content or Blood Alcohol Concentration, abbreviated BAC, is the concentration of alcohol in a person's blood.
BAC is most commonly used as a metric of intoxication for legal or medical purposes, and it's usually measured as mass per volume. For example, a BAC of 0.05% means 0.05 grams of alcohol per 100 grams of a person's blood, or 0.5 grams of alcohol per 1000 grams of blood.
Factors that affect your BAC include the following:
- 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.
- Drink Strength – The more 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. According to the Mayo Clinic, alcohol intolerance is caused by a “genetic condition in which the body is unable to break down alcohol.