Why blood sugar can be high in the morning

In the hours before waking, roughly between three and eight in the morning, the body releases hormones that prompt the liver to put more glucose into the blood. It’s a normal process, and it happens to everyone. It’s how the body gets ready to be awake.

In diabetes, there may not be enough insulin available to match it, so the effect shows up as a rising number over the last hours of sleep.

This is called the dawn phenomenon, and clinicians know it well. In a 2026 survey of 317 healthcare professionals, 96% were familiar with it, and they estimated that 20 to 25% of their patients on insulin experience it on a recurring basis.¹

The intuitive response is more basal insulin. The difficulty is that the extra insulin is present all night, not only during the hours the rise happens. More insulin at three in the morning, when glucose may already be at its lowest, moves the risk rather than removing it.

That’s the bind. The dose that fixes the morning can create a low at night, when you are least able to notice it.

Asked what matters about overnight and morning glucose, people rank avoiding lows first, then waking in the range they want. The average level people name is around 100 mg/dL.²

Both at once is the goal, which is why the overnight window is treated as a single problem rather than two separate ones.

This page explains a well-described physiological pattern. It is not guidance about your own insulin. Basal adjustments are a conversation for you and your clinician.