Hi China,
Good luck with your ankle op, I do hope all goes well for you. Well done on the HbA1c results.
Regarding Metformin, the best thing to do is discuss this with your GP or practice nurse. My GP lowered my dose of metformin because I had hypo's, he told me to leave off the night dose as my bg lows were occurring early in the morning. The other reason they might consider is if you have consistently good control and bg results or bad side effects. Why not take a log of your own bg results and a food/symptom diary and discuss what you would like to do with your doc.
An op is trauma to your body and can higher bg levels so this would need to be taken into consideration by the hospital team. There are certain procedures where Metformin has to be stopped 48 hours before, (have a look at the leaflet that comes with your medication). You should ask your doc if this is likely to be the case when you have your ankle op and if all goes well with the bg control they might let you start back on one a day but it's best to ask them. Medication and diabetic control is an individual thing and what works for one may not work for others.
I am using two walking sticks to get about and can't do foot/leg exercise but can still do upper limb exercises. A good workout can use up quite a few calories too. If they offer you physiotherapy. they should be able to show you a few good exercises to suit you.
Hope this helps a bit
x