I suffer from rheumatoid arthritis. When I was in Switzerland during Ramadan I wanted to climb a mountain. The distance between it and the place of residence was not more than 83 km but we climbed to the top and as the sun was rising I decided I wouldn't fast because I was afraid I would be too weak to continue my internship work and my immune system would crash. What should I do about the missed fast day?

You must make up the fast you missed on that day only.

And God Almighty knows best.