Not unless you were requested by v.o. to do so. If you stayed in a country, which is listed in the CIC website that requires a medical examination, for 6 months then you might be contacted by the officer and be asked to undergo a med exam. But it depends - since we're in UAE, many are given the visa without having this.
If you wanna make sure, upfront medical exam is optional. You can check the website for the list of approved panel physicians by the embassy. I tried it during my first attempt for a visa, but I wasn't allowed to cause I had no hold yet of the client number (to be sent to you by embassy for the exam) required to undergo the exam.