Ask your doctor.

You're pre-diabetic, that means your blood sugar is high. Nurse the gels slower when you're under load, or move to Clif Shot Bloks and eat 1 at a time instead of 3. A little alcohol (a glass (=4oz! NOT a 10oz goblet!) of wine, an ounce of whiskey, one beer) once in a while somewhat helps with glucose tolerance.

Seriously though, ask your doctor. You don't want to pre-load if you're pre-diabetic, because your pancreas is failing its insulin reaction. When I pre-load, my body stores lots of sugar as glycogen; when you pre-load, your body goes "uh... ok..." and struggles. When you're already under high metabolic demand, though, the glucose goes quick; your insulin reaction isn't as dramatic or important anyway. But it's still stressful.

See how this is difficult? Doctor will still be taking shots in the dark, but he's had a lot more experience with this stuff and studied it more than I have.