I don’t have ketones in my urine. Does this mean I don’t have to worry about hyperglycemia (high blood glucose)?

Not necessarily. It is possible to have dangerously elevated blood glucose without ketones, especially in people with Type 2 diabetes who are dehydrated. This is called hyperosmolar hyperglycemic state, and its symptoms include excessive thirst, hallucinations, sensory loss, rapid eye movement, paralysis on one side of the body, and seizure. It may be mistaken for a stroke.