Dawn phenomenon
A natural early-morning rise in blood glucose, driven by overnight hormones.
In the hours before waking, the body releases hormones (cortisol, growth hormone) that nudge the liver to put out glucose, readying you for the day. This can lift fasting glucose even though you haven't eaten.
It's normal to a degree; a pronounced morning rise is worth noting and discussing with a clinician. It's distinct from the Somogyi effect, a rebound high after an overnight low.