I use All Clear insurance but it was worth shopping around
You will need a copy of your prescription and a letter from your GP (both of these should be in same name as your ticket.
Take double the amount of equipment you'll need, invest in a cool bag, make sure you have a hypo kit.
When you go through security tell them you are diabetic and have medication and sharps on you.
Don't pack meds in hold luggage, take it with you as hand luggage.
Take a supply of snacks
You may need to change the timing of meals and insulin .
Most of all have a great time and take lots of photos