Hyperglycemia is the clinical term to refer abnormally high blood glucose (blood sugar) level. A high blood sugar is generally over 100 mg/dl. Hyerglycemia would be 150 – 300 or more. Related terms:hyperglycemia and vertigohyperglycemia vertigovertigo and hyperglycemiacan high blood sugar cause dizzinessDKA and vertigodka vertigo