While continuously tracking my blood glucose for two weeks I was surprised to observe a morning spike usually between 4am – 7am for me. It was consistently happening each day and seemed strange since I had not eaten any food for nearly 16 hours. I had expected my blood sugar to be lowest upon waking up. What was happening to me is known as the dawn phenomenon.

Via Diabetes Self-Management:

Organs do this to keep blood glucose from going too low at night or other times of not eating. From about 2 AM to 8 AM, most people’s bodies produce hormones, including cortisol, glucagon, and epinephrine. All these hormones increase insulin resistance and tell the liver to make more glucose. The idea is to get you enough glucose to get out of bed and start the day. The whole process is apparently started by growth hormones.

Everyone has a dawn phenomenon. Otherwise they’d be too weak to get breakfast. But in people without diabetes, insulin levels also increase to handle the extra glucose. People with diabetes can’t increase insulin levels that much, so their early morning blood glucose levels can rise dramatically.