Hi
I have had a few operations, and kept my insulin in my bag, also did my own test unless they really want to check themselves. They may suggest you don't take any insulin if you are put on a sliding scale, this is usually done with you having a canula in the hand and on a sort of pump. Depends what the reasons behind you being in there. One thing i would worn you about make sure if your kept in one position that you don't get bed sore on your heels, as this happened to me.
I shouldn't think they need to take your insulin away, but please remember they treat us all differently, just be confident in the way you tell them you know what you are doing.
Take care, hope all is well
Tracey