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Blood alcohol concentration

blood alcohol concentration (GB)

Amount of alcohol contained in venous blood (BAC), expressed in milligrams per gram or in per mille (1 per mille = 1 g alcohol in 1 kg blood or 1 mg/g). The measurement is taken in serum (blood without blood cells and coagulation factors) and is converted to blood content. The enzyme ADH (alcohol dehydrogenase) is used to determine the blood alcohol. This makes it possible to determine any impairment of concentration and sanity caused by alcohol. The taking of a blood sample can be enforced by a court (not enforceable in Austria - however, legally the same consequence follows as if one had been heavily intoxicated). To determine the BAC on corpses, blood may only be taken from the inguinal vein. Alternatively, eye chamber fluid may be used.

Widmark formula

The Swedish chemist Erik Widmark (1889-1945) developed the "Widmark formula" named after him in 1922 for determining BAC. In addition to Widmark's formula, there are other calculation methods named after the "inventors" (Seidel, Ullrich, Watson) that take body length and age into account in addition to body weight and gender. The Widmark formula is used as the basis for electronic BAC determination devices. With the help of this formula, the blood alcohol content can be calculated with an accuracy of plus/minus 0.1 per mille: c = A / (r * G)

  • c: blood alcohol content in per mille
  • A: absorbed alcohol in grams
  • r: distribution factor in the body (water in the body) = 0.7 for men and 0.6 for women
  • G: body weight in kilogrammes

Alcohol absorption in the human body

Since alcohol is exclusively water-soluble, it does not distribute itself in the bones and fatty tissue, therefore this body mass factor is not available. The factor is lower for women because they have a higher body fat percentage on average. Men, too, should assume a correspondingly lower weight G if they are overweight, since body fat, contrary to often expressed opinion, is neither conducive to distribution nor to the breakdown of alcohol.

Absorbed amount of alcohol in grams = V * e * p
To calculate the mass of alcohol (A) in a liquid (beer, wine, schnapps), the volume (V) of the drink measured in decilitres must be multiplied by the alcohol content in percent by volume (e) and the density (specific gravity) of alcohol (p = 0.8 kg/l or 0.08 g/cl). For a litre of wine (100 cl) with 12% alcohol by volume, the 12 cl of alcohol present in this case correspond to a weight of 96 g. Three glasses of cognac with 4 cl each result in 12 cl of cognac (a little less than "an eight"), which is 4.8 cl of alcohol with a weight of 38.4 g at 40% vol. alcohol content. So for the calculation, multiply the amount of the drink in cl by the alcohol content in vol% and then by 0.08. Two calculation examples:

A man weighing 85 kilograms and a woman weighing 70 kilograms each enjoy three eighths of wine (0.375 l = 37.5 cl) with 12% alcohol by volume: 37.5 * 12 * 0.08 = 36 g alcohol

reduced body weight = body weight in kg * distribution factor:
Man with 85 kg: 0.7 * 85 = 59.5 kg
woman with 70 kg: 0,6 * 70 = 42,0 kg

Alcohol level = alcohol / reduced body weight
Man 36 g / 59.5 kg = 0.60‰ - best assumption 0.38‰
Woman 36 g / 42.0 kg = 0.86‰ - best assumption 0.59‰

Determining the BAC - promille calculator

There is a large offer to calculate the BAC by means of a promille calcul ator (click) according to Widmark's formula after the consumption of alcoholic beverages on the basis of weight, body height and sex as well as the consumed beverages.

Alcohol breakdown in the human body

Any alcohol breakdown is not taken into account in the first value. Nor does it take into account the fact that 10% and 30% (on average 20%) can be deducted from the amount, since the alcohol is not completely absorbed by the body. If one assumes these 20% as well as a degradation of 0.1‰ each, the "best assumption" results.

The consumed alcohol passes from the stomach (20%) and small intestine (80%) first into the bloodstream and then into the body tissues. The distribution depends on the amount of blood (approx. 5 to 7l) and the body size or body surface, the more extensive, the better the alcohol is distributed. Fatty tissue, as already mentioned, cannot absorb alcohol. Therefore, in a large, lean person, alcohol is distributed more and there is less alcohol concentration in the blood compared to a small, obese person. The absorption is relatively slow and, depending on the contents of the stomach, is only completed one to two hours after the end of drinking. This amount is also called residual alcohol.

The liver is the only organ that can break down alcohol up to 90%, the rest is excreted through the kidneys with the urine or sweat. The organ begins to break down alcohol at the earliest 15 minutes "after the first sip" and continues to do so continuously regardless of further consumption in a linear fashion. The more someone is used to alcohol, the higher the elimination rate. The human body breaks down 0.1 to 0.2‰ per hour. A thumb formula: Half a litre of beer (5% vol) or an eighth of wine (12% vol), each containing ~12 mg of alcohol, is broken down in one to two hours. A faster reduction of residual alcohol is not possible through coffee consumption, increased exercise or sleep. See also under health.

Source: WIKIPEDIA Blood alcohol concentration

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Dr. Christa Hanten

For my many years of work as an editor with a wine and culinary focus, I always like to inform myself about special questions at Wine lexicon. Spontaneous reading and following links often leads to exciting discoveries in the wide world of wine.

Dr. Christa Hanten
Fachjournalistin, Lektorin und Verkosterin, Wien

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