Blood alcohol contentSouth Africa

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199. Blood alcohol content

Blood alcohol content (BAC), more precisely called blood alcohol concentration, indicates the amount of alcohol present in a person’s blood. It is commonly expressed as a percentage, grams per litre or parts per thousand (‰). Alcohol can impair judgement, reaction time, coordination and vision even before the legal BAC limit is reached. Legal limits vary between countries and may be lower for professional, novice or young drivers.

What is blood alcohol content?

Blood alcohol content (BAC) measures the concentration of alcohol in a person’s blood and is used to assess alcohol consumption and legal driving limits.

How is blood alcohol content expressed?

BAC can be expressed as a percentage, grams of alcohol per litre of blood or parts per thousand (‰). The units commonly used depend on the country.

What does 0.5‰ BAC mean?

A BAC of 0.5‰ means 0.5 grams of alcohol per litre of blood, which is equivalent to 0.05% BAC.

Is BAC the same as breath alcohol concentration?

No. BAC measures alcohol in the blood, while a breath test or breath analysis measures alcohol in exhaled air. Legal systems may establish corresponding limits for both measurements.

Does everyone reach the same BAC after drinking the same amount?

No. BAC can be influenced by factors such as body composition, sex, the amount and speed of drinking, food intake and the time since alcohol was consumed.

Can alcohol affect driving below the legal BAC limit?

Yes. Alcohol can impair driving ability before the legal limit is reached. Being below the legal BAC limit does not guarantee that a person is safe to drive.

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