Hyperosmolar hyperglycemic state (HHS) is a serious medical condition that develops if your blood sugar levels get very high. Your body gets rid of the extra sugar through your urine. This leads to severe dehydration. HHS can occur in people with type 1 or type 2 diabetes, but is more common in people with type 2 diabetes. What causes HHS? HHS usually develops because of other illnesses or conditions that cause blood sugar levels to rise, such as the following: Not taking insulin or diabetes medication as directed