Diabetic here, also. Type 2 of many years. Learned it's the large "swings" in sugar/food in general that are most harmful/symptomatic - either high or low. Too low is as harmful as too high as far -as shakes/fatigue. Better results with smaller portions frequently through the day in moderation.
Also, regardless of strength, it is not humanly possible to hold a firearm on target without movement, (even nearly imperceptible) without a support. We can lessen the movement, but there will always be some. Typically, movement will be circular. Practicing stage-firing with a glass-smooth trigger allows the shooter to complete the trigger pull at nearly the same time with every shot, greatly increasing repeatability and thus tightening groups.
Diabetic fatigue and tremors just plain suck. So does loss of sensory perception in fingers and blurry vision. Don't give up. You're not the only one.