Recovering PD/borderline T2D here--and 3-time Whitney dayhiker. I never worry about eating carbs before or during a strenuous hike like Whitney--in fact, my hiking "food" has devolved to sour gummy bears and butterfinger bites because I just don't crave nuts/cheese/jerky/bars on the trails.
If your D has progressed to the point where you need meds/insulin, I expect it would be best to consult your doctor beforehand, and to test out your regimen on tough training hikes where you are closer to medical services if need arises.
