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July 25, 2003

Daily Care

Question from Vernon, Texas, USA:

I am over 60 years old, and I want to know what is the cause of dawn phenomenon in a person my age.


The term dawn phenomenon was originally applied to the change in circadian rhythm of glucose metabolism that was noted in normal persons and consisted of a rise in blood sugar between about 5:00 and 9:00 am that was due to an increase in glucose release by the liver. It was accompanied by an increase in serum insulin. Several studies confirmed this change in type 1 but not in type 2 diabetes.

In recent years, the phrase has come to be applied to any inappropriate rise in blood sugar before breakfast in subjects taking insulin.Thus insufficient insulin before supper to cover the night hours may be a cause of this, but more frequently perhaps it has an opposite basis when too much evening insulin for any reason leads to early morning hypoglycemia that is then followed by a compensatory mobilisation of blood sugar from glycogen stores and gluconeogenesis that is triggered by what is called the counterregulatory hormone release. This response may overcompensate and raise the blood sugar above well controlled limits. This aspect of the phenomenon is reduced by a change in insulin regimen.