“The dawn phenomenon, sometimes called the dawn effect, is an early-morning (usually between 2 a.m. and 8 a.m.) increase in blood sugar (glucose) which occurs to some extent in all humans, more relevant to people with diabetes.”– from Wikipedia, the free encyclopedia.

When you wake up in the morning, the body needs to shift gears.  When you’re sleeping, your body is in rest and repair mode, called parasympathetic function.  When the sun comes up and you start your day, you shift into sympathetic function.  The body gives us a little burst of energy from various hormones, which raise blood sugar and activates our muscles, and senses.  Without this, most of us would be too weak and foggy-brained to get out of bed and get going.

People who don’t have diabetes are, of course, at an advantage, because as their blood glucose increases, so does insulin, and their livers are sensitive and responsive to that insulin. People with diabetes and blood sugar problems don’t properly respond to insulin, so their early morning blood glucose levels can rise dramatically.

If these early morning blood sugar spikes aren’t caused by food, what is the cause?

Although the exact underlying causes of the dawn phenomenon are still unclear, it is known that hormones, including adrenaline, cortisol, glucagon, and growth hormone, play a large part. These hormones follow a circadian rhythm, or a daily cycle, and tend to be found in higher concentrations in the blood in the morning to help prepare us for the day ahead.

The hormones that promote glucose release into the blood include:

  • Adrenaline: Known as the “fight or flight” hormone, adrenaline increases blood flow to the muscles and promotes the release of glucose into the blood.
  • Cortisol: Known as the “stress hormone”, cortisol also plays a role in increasing blood glucose.
  • Glucagon: Signals the liver to release glucose into the blood.
  • Growth Hormone: Important for repair and regeneration and promotes the release of glucose into the blood.

Two key processes occur in the liver overnight that result in the release of glucose into the bloodstream and contribute to increased morning blood glucose:

1) Glycogenolysis, the breakdown and release of stored glucose (a.k.a. glycogen)

2) Gluconeogenesis, the creation of glucose from components of protein (i.e. certain amino acids) or fat (i.e. glycerol)

One more hormone that plays an important role is insulin. When blood glucose rises, insulin is released and helps move glucose out of the blood and into cells for energy use or storage.

Does the dawn phenomenon occur only in people with prediabetes and type 2 diabetes?

The physiological processes that underlie the dawn phenomenon occur in everyone regardless of whether they have diabetes or not. The difference lies with insulin and how our bodies react to it. Healthy individuals secrete enough insulin and are insulin sensitive enough to counteract a rise in morning blood glucose. However, someone with prediabetes or type 2 diabetes is insulin resistant and/or may not secrete enough insulin, which allows blood glucose to rise. This may be further compounded in the early morning hours because our body is more insulin resistant compared to the rest of the day, causing an elevated fasting glucose to remain elevated longer. Progression of prediabetes and type 2 diabetes is likely to result in a worsening of the dawn phenomenon as insulin function and sensitivity continue to diminish.