Why am I getting hypoglycemia almost every time I work out?

I am not a diabetic, but I bought one of those glucose machines because I thought this was happenign to me, and I was right. About 50% of the time when I do my 30 minutes of cardio, I get hypoglycemia about 15 mins into it, or sometimes at the end. Usually I start feeling anxious and my vision gets darker. My workouts are normal moderate intensity for my age (31). I have numbers like 62, 56, and even 42 once. I have had to resort to keeping a soda on the table next to my exercise bike. Even after the sugar is corrected, I still feel mentally anxious for a good long while. I always eat within an hour of starting my workout. Stuff like oatmeal or cereal, a piece of fruit or juice, and a couple of eggs. Never any sugary stuff, just plain oatmeal/cereal. My Dr. has drawn a CBC and metabolic panel on me recently and they are normal.