The Dawn Phenomenon and Somogyi Effect
Here are two other situations that may cause high fasting blood glucose levels:
Dawn phenomenon happens as part of the body's normal circadian rhythm to wake up and get going. Hormones, such as growth hormone and cortisol, are released and raise glucose. Without diabetes, the body simply responds to this early morning effect by putting out more of the hormones that keep blood glucose in control. That doesn't happen when you have type 1 or type 2 diabetes.
Somogyi effect is very high fasting blood glucose thought to be caused by the liver making a lot of excess glucose in response to hypoglycemia (low blood glucose) during the night. Somogyi effect is uncommon in type 2 diabetes. There's controversy as to whether it even exists with the rapid- and long-acting insulins available today.
Hope Warshaw, R.D., CDE, coauthored Real-Life Guide to Diabetes (American Diabetes Association, 2009) and is a contributing editor to Diabetic Living.