Dawn phenomenon is a rise in glucose (blood sugar) in the early morning. This occurs naturally in everybody, but in people with diabetes it can result in abnormally high glucose (hyperglycemia).

Dawn phenomenon usually occurs between 4 a.m. and 8 a.m. Overnight the body releases a group of hormones known as counterregulatory hormones. These natural chemicals signal the liver to release glucose into the bloodstream and suppress the activity of insulin, causing glucose levels to rise.

In most people, glucose rises just enough to provide the body with the energy necessary to wake up and begin the day. A burst of insulin handles any excess glucose. However, people with diabetes either do not produce insulin (type 1 diabetes) or cannot properly use available insulin (type 2 diabetes) to respond to this rise in glucose. As a result, glucose continues to rise and causes hyperglycemia.

To adapt to dawn phenomenon, patients may be advised by their physician to make changes in their treatment plan such as adjusting their diet, glucose monitoring, medication or exercise.