Quite often, your liver starts pumping out extra glucose just before and after you get up a morning, to prepare for the coming day, this is the Dawn Phenomenon that Mark referred to above. Some people find that eating something for breakfast straight way stops it in its tracks, and they end up lower a couple of hours later. It varies from person to person, so trial and error is the only way to find out. ( If I remember my kid's school maths lessons, it's now called Trial and Improvement, because we wouldn't like to tell them they were making an error, now would we!)
Personally, I find that caffeine raises my glucose levels, so Coke Zero and a coffee would have my levels hitting the stratosphere,