Altitude sickness on Rail Tour

I don't think you can get sick anywhere a train can go. The peaks, perhaps, but trains operate in the valleys.

This might help (from UK NHS)
https://www.fitfortravel.nhs.uk/advice/general-travel-health-advice/altitude-and-travel

What part of this rail tour is "high altitude"? I would think that it must be a side trip, like to the Jungfraujoch or Matterhorn Glacier Paradise. If that is the case, you could always skip these. Otherwise, the Oberalp Pass is 6700 ft, and the Bernina Pass is 7600 ft, I don't see anything higher on regular rail lines in Switzerland.

Over hydrate before, during and afterwards and if you're really struggling then just ride the train back down to a slightly lower altitude and symptoms will subside.

While in an airplane the cabin is pressurized to a little under 8,000 ft, so if you can be in a plane, then you can be in mountain areas at that level, which is very easy to get to amidst the higher mountain experiences. For example, Jungfraujoch you can descend down to Eigergletscher or Kleine Scheidegg. Schilthorn, you can descend down to Murren. Gornergrat you can descend back down to Zermatt. Nowhere is going to have you "stuck" and in some sort of emergency.

This is our first rail tour and I'm concerned about altitude sickness.
I've had it before at 10K feet in the US. There will be 2-3 high
altitude train trips in this potential package. Any advice?

Talk to your doctor. They may advise you to take some tests before travelling or that you can't take certain routes. I've lived in Switzerland for over 30+ years and in recent years I've had to stop taking certain routes on the advice of my doctor and after taking some tests.

Thank you Jim. I appreciate your candid reply.