If you are 21 years of age your blood alcohol level can not register what number?

If you are 21 years of age in the United States, your blood alcohol concentration (BAC) cannot exceed 0.08% while operating a vehicle. A BAC of 0.08% is considered the legal limit for driving. For individuals under the age of 21, any detectable level of alcohol in the blood can result in penalties due to zero-tolerance laws.