If you have a medical condition, do not tell Air Canada before you take off.
We were removed from a flight due to a misinterpretation of Air Canada's health safety guidelines. My son has a nut allergy. Their rules had changed and some idiot decided that we needed to get medical clearance from Air Canada's Medical department.
On the phone the next day, Medical told me that the flight crew had made a mistake, as my son does not have a problem with airborne contagens.
I tried to explain this to the flight staff, but they held the flight up for half an hour to get us off the plane. They were going to remove our luggage, but I told them not to bother as I felt we had disturbed the flight enough.
So my wife, and other three children went back to Sydney and we followed a day later. I am sure you can imagine the amount of inconvenience this caused our entire family (wife had to handle extra luggage, changed travel arrangements to get home, rescheduled meetings, etc, etc.), as well as distressing and embarrassing my son.
Not impressed with Air Canada.