I'm a T1 diabetic, for over 30 years. I've once been challenged over my Insulin at that time simply involved the security guy walking me down to my gate and giving my 'pen' to the gate agent. As soon as he disappeared around a corner the gate agent gave it back to me simply rolling her eyes.
One thing to be careful of though is ice. At Heathrow the other day the lady in front of me had some medicine that needed to be kept cold. They poured out the ice, and pointed her in the direction of the nearest restaurant and told her she could get some more there.
If cooling is an issue - try
these guys. I've used their products for years and keeps things cool - not cold.