Where does one report horrible doctoring in Illinois?

I don’t want to go into detail, and it’s not my place to - this is a person in my life who got horrible (according to another doctor, potentially fatal) advice about a prescription med.

Googling gave me pages of malpractice lawsuit links.

Right now I’m looking for a state entity (medical review board?) that one can contact. Probably an easy, dumb question, but I can’t find what state agency would be interested.

Thanks.

In Illinois, the Division of Professional Regulation handles licensing of physicians and other professionals. They have a complaints link on their website.

Thanks.