Ethanol is cleared at an approximate rate of 15 mL per hour (healthy, nonalcoholic adults will clear 1 drink per hour).
1 standard bar drink (1.5 ounces of 80 proof liquor) = 1 standard glass of wine = 1 bottle of regular (4.5%) beer.
- Alcoholics clear ethanol faster than normal.
- Alcohol concentration is performed by headspace gas chromatography with flame ionization detection (GC-FID) (reference method to demonstrate intoxication potential in blood).
- Serum may be submitted, but is not preferred.
- Urine alcohol concentration is not a good indicator of intoxication.
Note: Urine alcohol concentration depends on a number of alcoholic drinks consumed, fluid intake, and number of hours since last voiding.
The Widmark Equation is a useful tool for:
- Predicting Blood Alcohol Concentration (BAC).
- Predicting time elapsed since the last drink.
- Estimating how many drinks were consumed if the time of the last drink and BAC are known.