The symptoms of hyperglycemia are similar, whatever the cause.
*First, once the glucose level is higher than the renal threshold, your kidneys will start spilling glucose and will use water to do it, so you're likely to be (or on the ways to becoming) dehydrated. This is not good.
*Second, as your blood glucose level rises, more water will be pulled (for straightforward osmotic reasons) from within cells into the blood. This will result in a sort of extra special dehydration of body cells. This is not good.
*Third, as part of the dehydration and the kidney's dumping water to keep the glucose level under some soft of control, electrolytes will be lost; these are small molecules or ions which are required for various functions including operation of every nerve in the body. This is also not good.