don't worry.
Just pick up where you left off with the metformin when you get home.
It is a drug that builds its effectiveness over time (something like 2-3 weeks, I believe), so while you would ideally take it every day, if you are consistent the rest of the time, 2 days off won't be an issue.
The problem with metformin is when people don't take it consistently, because then it doesn't get the chance to build up, and then they don't get the benefit from it.
Hope that helps.
I'm not familiar with saxaglipton, so can't comment on that one.