Could be. However, it's typically associated more with low blood sugar than high. Diabetes symptoms include (but are not limited to) blurred vision, increased thirst, frequent urination, and fatigue.
Yes, dizziness is a sign of diabetes - low or high blood sugars. But, it also is associated with a number of other health issues that only thorough testing can uncover; a stroke, balance disorder, inner ear inflammation, a tumor and so on. Go see your doctor for proper evaluation and treatment. Good luck -