Hey,
If going on a plane ensure you get a letter from your nurse/gp to explain the needles, insulin and sugary snacks in your hand luggage!
If going somewhere warm I would check there is a fridge in the building you are staying one. I don't book anywhere unless I know there is a fridge! Maybe also invest in a frio cooling wallet as these are great for warm weather or public transport and cars that may be of an insulin damaging temperature!
I would always take more supplies than you need - and spares such as battery for glucose meter. I over stress when it comes to this but I would rather be too prepared than run out of something in an unfamiliar location!
Enjoy your travels