Have you recently had a medical? If not, then you would need to have one. I don't know if a very recent medical would need to be repeated. See section 5 of http://www.cic.gc.ca/english/resources/manuals/op/op15-eng.pdf
In that case, yes, you must have one, and so must all your dependants, if any.
5.1. Who Must Undergo an Immigration Medical Examination?
Foreign nationals required to undergo immigration medical examination are outlined in
R30(1). These include:
foreign nationals who are applying for a permanent resident visa or applying to
remain in Canada as a permanent resident as well as their family members, whether
accompanying or not;