In Chicago, the legal BAC limit for drivers 21 years and older is 0.08%. However, for commercial drivers, it's 0.04%, and for drivers under 21, any amount of alcohol is illegal.

In Chicago, penalties for DUI offenses escalate with each subsequent offense within an 84-month (7-year) timeframe. For a first-time DUI offense, individuals may face a minimum of 10 days in jail, around $1,500 in fines, a 90-day license suspension, and mandatory installation of an ignition interlock device for 12 months. An "Extreme DUI" with notably higher BAC can lead to a minimum of 30 days in jail and roughly $2,780 in fines. A second DUI offense could result in a minimum of 90 days in jail, fines nearing $3,500, a 12-month license revocation, and the ignition device's continued requirement. Second offenses with higher BACs have even steeper penalties. By the third DUI offense and any subsequent within the 84-month period, the charges generally escalate to felonies, often termed "Aggravated DUI", with penalties including a minimum of 4 months in prison, extensive fines, a 12-month license revocation, and a 24-month requirement for the ignition device. Of course, each case is different and nature and this should just be viewed as a general guideline.

This is an immediate suspension of driving privileges if you are arrested for DUI with a BAC of 0.08% or more, or if you refuse a BAC test.

You have a right to refuse the breathalyzer and/or blood test, but Chicago has "implied consent" laws. Refusing a test can result in a 12-month suspension of your driving privileges and might be used against you in court. Additionally, a warrant can be requested by arresting officers for your blood sometimes making the decision worse than if you did participate in the request.

An IID requires a driver to blow into it before starting the vehicle. The car won't start if alcohol is detected. In Chicago, even first-time DUI offenders may be required to install an IID. The length of time depends, but it is generally for 12 months for a first-time DUI.

Depending on the circumstances, you might be eligible for a restricted license after a certain period following your suspension.