I'm an ardent hillwalker and climber, and type 1 diabetic for 35 years (since I was 1, so can't really remember anything else). If you do regular strenuous exercise, climbing a mountain shouldn't cause too much havoc with your diabetes. However, as I do this on a daily basis, I'm not sure how helpful I can be if you're just starting out. I always keep copious amounts of dextrose tablets in my bag, and am aware that the problems (if any) tend to come towards the end of the day, once your resources are running low, and you're making a dash to get back to the car. Also, be very careful with the basal insulin, it can keep low blood sugars going for ages when ascending a hill. But I honestly can't see how diabetes should keep you away from the hills. I'm also a member of the Skye Mountain Rescue, and can say that poor equipment choice and lack of navigation skill is a much bigger concern than diabetes.