High blood sugar feels very different and much more subtle than low blood sugar. If anything, it feels heavy and sleepy, and you have to pee a lot because your body is trying to dump the excess sugar into your urine. This is why, many years ago, before modern science, one of the first things people observed about diabetes is that it made your urine smell or taste sweet, and where the word mellitus comes from: the latin root for honey or sweet.
As a result of all the urination, high blood sugar also usually makes you feel dry and thirsty.
As opposed to low blood sugar, which needs to be addressed urgently or you could go into a diabetic coma and die, high blood sugar is dangerous only after years of prolonged exposure. Basically, the sugar thickens your blood, preventing it from flowing perfectly into the smallest capillaries, which then don’t receive the proper oxygen from your blood and slowly die. The first complications of diabetes appear in organs with the finest mesh of capillaries, such as your eyes and other organs.
Sugar crystals in the blood can also rip cells apart, which is why it’s often advised to not exercise vigorously when your sugar is very high (above 300), despite the fact that this would help lower your sugar. I usually just take a little short-acting insulin until my sugar level returns closer to normal before starting to exercise.
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