What Causes Dizziness And Light Headedness?

Over the past 3 weeks I have been experiencing dizziness/light headedness, weakness, and random sweating. After having these symptoms for 5 days straight, I went to urgent care and was told that my hemoglobin was one number off from being diabetic and that I needed to change my diet. The problem is, I'm already really thin, exercise several times a week, and eat healthy so i'm not convinced that its related to blood sugar?? since then I have randomly had these symptoms for no apparent reason.