If your blood sugar is higher than 600 milligrams per deciliter (mg/dL), you have a condition called diabetic hyperosmolar hyperglycemic syndrome. In an effort to cope with too much sugar in your bloodstream, your body releases it into your urine and takes lots of fluids away along with it. You need treatment quickly to get hydrated so you don't get seriously dehydrated. At worst, you could end up in a coma or even die.
Hallucinations -- when you see and or hear things that aren't there -- are one sign of this syndrome. When you're very dehydrated, the balance of essential minerals in your body (called electrolytes) gets out of whack. That can affect the communication between your brain cells and lead to hallucinations. Once your doctor is able to rehydrate you and lower your blood sugar, the hallucinations will end.