Why do I keep on feeling dizzy? What can I do?

I was feeling a little dizzy before lunch, a few hours after I ate breakfast. Thinking it was my blood sugar, I drank a sugary juice and ate a little bit of icing, and that seemed to help. So I made myself a big lunch, thinking it'd help more. I'm dizzy again, and I don't understand why. I've been sipping on sugary juices and it doesn't help. Anyone have any ideas on what else I can try?