As I understand it, in the UK at least, testosterone is given either as a gel, which is rubbed, daily, into the skin (upper arms/chest/belly) or as an injection into the buttocks given quarterly. These are compatible with T2 diabetes and are provided, when appropriate, on prescription, by a doctor.
The way you have worded your query, "take a testosterone supplement", I wonder if you are obtaining something (a pill?) privately, not via a doctor. Is this wise? Testosterone is a powerful hormone and should only be administered when your natural levels are low. Many T2 males can be Low T, but it needs to be checked. Getting sugar levels sorted and re-gaining general health can sort the problem out, but a prescribed supplement can "help you on your way".
Sally