I'm not in a commercial company but I work in hospitals and at a university on the clinical/research side.
Hospitals, as far as I experienced, use commercial EHR software on Windows desktops or, better still, personalized web apps that run on everything, so many of them have Windows desktops everywhere and/or iPads to get things done at the bedside (some hospitals give an iPad to each doc and some to the nursing staff, so they are always and everywhere connected during the shift). The Office365 platform is heavily and widely used, especially Exchange, but this isn't much of a problem since I can sync most things with my Apple personal devices (which I obviously don't use with the EHR and patient's data, maybe in the future it will be possible but at the moment I see too many security problems).
The university makes heavy use of the Office 365 and of the Azure platforms. I can access resources and get work done from Windows or from macOS/iOS, so having only Apple personal devices is not a problem. Hardware is fully Windows as far it is provided from them, but a ton of us have personal Apple devices and we use them almost exclusively as the provided Windows 10 boxes are slow AF, have horrible keyboards and especially mices, and the list could go on.
I prefer using Macs because if I need Windows I can install it alongside macOS, create a virtual machine with it or RDP into a Windows computer. I've done all three things and they have worked really well, with an almost indistinguishable experience from that of native Windows hardware. On top of versatility I get great displays and powerful, beautiful all-in-ones as desktops and excellent battery life and great build quality on mobile, plus perfect integration between them and my iPhone. In the end I'm interested in getting stuff done peacefully and quickly, especially when number crunching statistical data of trials and studies.
That said, equipping with Macs an entire hospital or university would be very costly and basically useless. I could see a small-to-medium practice going all-Mac, or a private group of providers, but iMacs in clinical settings would be basically wasted (I'm of the opinion that in clinical setting nothing more than an iPad is really needed... keyboards, mices and cables are a receptacle for bacteria and other crappy beasts, and we do very basic things with the software, except for the radiologists who need dedicated workstations... some get iMacs and MacPros, some get Lenovo, Dell or HP, with a majority toward the second for economic reasons).
More than this, most staff wouldn't get the difference between a fork and a cutter, IT-wise. New generations are better at this, many of them owned Macs when they were studying for their degrees and use an iPhone every other minute, so they have a basic idea of what software/icon does what, of the window management works (different full screen), how to right click, how to use shortcuts... but I see so many unbelievable things even with Windows that I'm not sure spending hundreds of thousands of whatever currency would result in a better level of care and more efficient time spent in front of the computers. This is why I think the iPads are the way to go: you just touch what you want to execute and you can't mess with the device or the OS settings, you don't have to power monitors on or off (scary stuff), you can't download your daughter's engagement party invitation PDF on the ward computer and you don't have to reboot that often (in some services I think we get months of uptime on some machines), and last but not least they use way less energy.
Anyway, that's just my take. I know of universities that use Macs everywhere, but I suppose they still have a lot of Windows-based apps and services, especially in the technical departments.