Tou are hyper, or fatigued, blurred vision, headaces, eventually not being able to hold down any food, vomiting and frequent urination. Cuts take longer to heal Your kidneys can fail. Your blood becomes acidic with ketones. You go into diabetic ketoacidosis, then diabetic coma, and death.
The opposite can happen from LOW blood sugar, hypoglycemia, and you can die much faster. You can act like you are drunk, and you can either be a happy drunk or a grumpy, angry drunk. From your perspective, your universe is unraveling. In many ways your brain is unraveling and shutting down. That's why there is an overwhelming desire to sleep.
64+ years personal life diabetic experience being a type 1 since 1955. I was 2 years old. when I was diagnosed.