Dawn Thropp faces a felony count of unlawful possession of a medical transport vehicle, officials said.
According to authorities, the private ambulance was reported stolen around 6:45 a.m. Tuesday from the UIC Medical Center ER bay in the 1700-block of West Taylor Street.
The suspect drove the ambulance down the outbound Eisenhower Expressway to Hillside, then got on the southbound Tri-State Tollway and drove to Alsip, near Cicero Avenue, police said. There, she stopped the ambulance in the right lane of traffic and was arrested peacefully just before 8 a.m.
Medical Express Ambulance Service owns the ambulance that was stolen.
"We're just fortunate that nobody was hurt and that the authorities are now investigating," Frank Nagorka, a Medical Express Ambulance Service attorney, said.
Nagorka said the vehicle sitting outside of the hospital was locked, but the suspect was still able to get inside, drive off and operate the lights.
"They are sophisticated vehicles. Thousands of pounds. People give way to them," he said.
The ambulance company is looking into how to prevent something like this from happening again.
"We have a lot of security measures, but as you can imagine, all security measures can be circumvented and we're still investigating how that occurred today," Nagorka said.
The ambulance is back in service.