as daibell says, never put insulin in any hold luggage. Also if you're travelling with someone else, split your medical supplies 50/50 and also take twice as much as you think you'll need - just in case.
I double up on insulin, needles and tablets etc, the wife will carry half of it and my basal insulin pen and I'll carry the other half with my bolus pen, plus spare one. Worse case scenario, my bag gets nicked I can swap the insulin in the basal pen as and when required (along with the needle!).