When blood sugar levels remain high for a period of time, it can lead to dehydration, which causes dizziness, the National Library of Medicine explains. The kidneys filter extra sugar from the blood and expel it from the body, but they use water to dispose of the waste. If the body doesn't replace that water, dehydration occurs. This dehydration can cause dizziness, disorientation or even the life-threatening diabetic ketoacidosis, according to eMedicineHealth.
A healthy adult may be able to cure mild to moderate dehydration by drinking water or sports drinks, reports the National Library of Medicine, but hyperglycemic dehydration can be much more serious. As blood looses water to the kidneys, the glucose levels become more concentrated. Water leaves the brain and other organs to dilute the blood, but the kidneys use it to filter and expel more glucose. This results in hyperosmolarity and a cycle of increasing blood pressure levels and dehydration.
In addition to fluids and potassium, a patient with hyperosmolarity may need intravenous insulin to reduce blood sugar and break the cycle, notes Mayo Clinic. If the dehydration has progressed to nausea and vomiting, stomach pains, shortness of breath, or dry mouth, it's important to seek medical attention immediately.