when your application is successfuly passed (w/ or w/out interview), they will want to make sure everything is ok w/ your body system! To do so, you will be asked to undergo medical examination by a designed dr of CIC from your erea.
That would be at your own expense and will consist at : blood test, bp, chest rays, urine test, take your height & weight, see how good you can read from a certain distance w/ both eyes opened & one of each eye closed, check your testicles, routine questioning.....
all this is what happened in my case and might be different in some cases (not sure!!!).
In my case i paid $ 425 and it took me less than hour to undergo all that...it all depends on the erea and the dr.
hope this help!