Have a read up on Dawn Phenomenon (google will give you plenty to get an idea of it)
But it is worth remembering that we are all different. As Freema says, your fasting readings can be affected by what you ate the day before. However, they can also be affected by what you drank (alcohol) or what you have been eating for days before (think Xmas), or stress levels, or exercise levels, or sleep deprivation, or stress... the list is pretty endless really.
Morning fasting levels are often the slowest readings to respond to introducing a lower carb diet. Sometimes they can take months to subside.
Dawn Phenomenon is largely caused by hormones, and that includes stress hormones. So the more stressed you are, the more the effect will be.
For example, my fasting readings always shoot up if I have a job interview that day, or I know I have a busy/tight schedule, or if my sleep was disturbed. There was one memorable occasion when I was woken by hysterical screeching, looked out the window and saw foxes (parent and pup) going for a cat. Dashed outside waving the mop. Drove them off. And the next morning my fasting blood glucose was about twice what it should have been! lol.