According to research by Doximity 85% of doctors use an iPhone ... and it is probably fair to assume that almost all of the remaining 15% use a smartphone running Android given smartphone use is almost ubiquitous. This is completely almost completely reverse when compared to the general population.
According to IDC this is almost completely reversed when compared to the general population. In November 2016 it was 86.6% Android, 12.5% iOS and 0.3% Windows Phone, 0.4% other. (Not sure what happened to the other 0.2% but let's go with it.)