I've been diabetic for many years and wear an insulin pump. I don't take the pump off whilst being scanned. It will alarm the primary scan about 50% of the time which results in a pat-down. I've never had any issues with medical supplies, whether it be insulin or pills. I don't take any particular precautions to cool my insulin whilst travelling, but cool it when I reach my destination.
I believe that most insulin is much more robust than it used to be and I've never had any go off when travelling.