Depends on a number of things - is it GA or epidural, what insulin therapy are you on, etc etc. If you are using an 'all day one jab' basal insulin eg Lantus, you need to know whether to take it, and if so, how much, the night before the op, for starters. Is it 'Day' surgery, or what? You may be put on a 'sliding scale' (insulin pump operated by anaesthetist during op) or you may not, depending on how long the procedure is likely to take.
I had a hysterectomy in the hospital that was the main regional BUPA knee clinic. After about 4 days I said to the sister Oy - I want a word with you! Every day I see strapping young, fit blokes coming in here, and every day I see em after you lot have done your stuff on em going home again - and every man jack is either on crutches or in a wheelchair! Thought you were sposed to make em better!
Some of the beds had squeaky wheels - it was disturbing trying to recover after a major op, with the constant parade past my door - I mentioned it to my consultant and she told management who got the maintenance team in to sort it. Nurses said after they'd been moaning about it for years to no avail - but it makes a difference when a paying guest complains! I told them to report back that I was appalled it had taken me to say something to get something done and that I thought it was illustrative of poor show from Management ! Would have loved to be a fly on the wall.