hi! im living and working here in shanghai for almost 2 years now..i was diagnosed last year with type 2 diabetes and then just last week they found out it is really type 1. anyways i hope the info below are helpful to you:
diabetic supplies - wide variety available in almost any pharmacy. you can buy OTC and prescription supplies in big pharmacies and in small ones. supplies here are the good ones but its not that expensive. im using accu-check and novopen and it didnt cost me that much. OTC drugs too ( when i was a type 2 diabetic) dont cost much as well.
insurance - it differs actually from the insurance company of your employer. since you mentioned you plan to teach here, i have great news for you! teachers get big salaries here and they get good insurance packages as well. just verify this with your employer. mine dont cover diabetes though
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doctors/endocrinologists - i go to an international medical facility (sun-tec) and their staff are bilinguals. they have good command on the english language so you wont have trouble communicating with them (if you dont speak chinese.)
food selection - there are a lot of international supermarkets here so you can still buy foreign brands. local wet markets also sell good choices for vegies and fruits (and its cheap!)
that's all i can think of right now. currently i am still trying to control my blood sugar too 
dont worry you're not crazy
