UpToDate recommends citing entries or topics found on UpToDate as chapters in a book titled UpToDate.
The example given by UpToDate is as follows:
Marion DW. Pacing the diaphragm: Patient selection, evaluation, implantation, and complications. In: UpToDate, Post TW (Ed), UpToDate, Waltham, MA. (Accessed on January 04, 2018.)
Information on how to cite UpToDate in a presentation can be found here.