Understanding Blood Alcohol Concentration: Units, Limits & Lethal Levels

Units of Measurement

• % BAC (w/v): Grams of ethanol per 100 mL blood. Legal limit in most US states = 0.08% (80 mg/dL).
• mg/dL (mg%): Milligrams per 100 mL. 0.08% = 80 mg/dL.
• mmol/L: 1 mmol/L = 4.6 mg/dL. 0.08% ≈ 17.4 mmol/L.
• Promille (‰): Used in Europe. 0.08% = 0.8‰.

What About "492"?

The number 492 likely refers to mg/dL (0.492% BAC). This is not impossible—it represents severe intoxication (stupor, coma risk). Levels >300 mg/dL (0.3%) are potentially fatal; >400 mg/dL (0.4%) carry high mortality.

Highest Recorded BAC

Medical literature reports survival at extremely high levels. A widely cited case: a Polish man with 1.48% (1480 mg/dL) after a car crash (2013). He survived. Lethal levels are typically >0.4% (400 mg/dL) in naive drinkers; chronic alcoholics may tolerate higher due to metabolic tolerance.

Clinical Effects by BAC

BAC (% / mg/dL)	Typical Effects
0.02–0.05 / 20–50	Mild relaxation, slight euphoria
0.06–0.10 / 60–100	Impaired judgment, coordination, reaction time (legal limit)
0.11–0.20 / 110–200	Slurred speech, ataxia, mood swings
0.21–0.30 / 210–300	Confusion, dizziness, nausea, vomiting, blackout risk
0.31–0.40 / 310–400	Stupor, respiratory depression, loss of consciousness, death possible
>0.40 / >400	Coma, respiratory arrest, death likely

Safety

• Never drive after drinking. Impairment begins at 0.02%.
• BAC continues to rise after last drink (absorption phase).
• Only time lowers BAC (~0.015%/hr average). Coffee, cold showers, exercise do not accelerate elimination.