You can certainly get high blood glucose levels, just see what happens if you eat a large candyfloss :roll: normally though unless you neglect your control for some time hopefully you are unlikely to get the very high spikes as you have some insulin of your own to counteract it.
Anyone can get low blood glucose levels, my non diabetic husband gets them from time to time after hard manual work. However unless you are taking insulin or sulfonylureas a level just around 4mmol its nothing to be anxious about, the problem with those drugs are that if there is too much of them in the system they can quickly drive levels very low indeed.
Indeed Even on insulin a level of 4 isn't anything to panic about. Indeed this afternoon I was on a long walk and was beginning to feel a little low as I got to a steep hill, a few steps up it confirmed it, I hadn't enough energy, reading was 3.8mmol. I took 1 dextrose (4g carb) waited a few minutes and then continued the final 6k of the walk (with another dextrose about 40 min later).
I agree with the previous posters you probably feel shaky because you're not used to these very normal levels, just have a few carbs and carry on.