Blood sugar control in diabetic patients bearing microinfusors: the importance of the dawn phenomenon

Significant early morning hyperglycemia (the so-called "dawn phenomenon") has been observed in insulin-dependent diabetics who were otherwise well controlled. This phenomenon, if present, could lead to errors in adapting the basal insulin infusion in CSII treated diabetic patients, because a normal glucose level in the morning could be associated with asymptomatic hypoglycemic values in the night. In order to observe the occurrence and to quantify the magnitude of this phenomenon 14 well controlled CSII-treated type I diabetics were hospitalized for 1 night and samples for the determination of blood glucose (14 patients) and serum cortisol, free insulin and NEFA (8 patients) were drawn at 24.00, 02.00, 04.00, 06.00, 08.00 h. Blood glucose values were slightly but significantly higher at 06.00 than at 02.00 (106 +/- 7.92 v.s. 88.57 +/- 7.02 mg/dl, p less than 0.025, paired Student t test) while serum free insulin values decreased from midnight to 02.00 and then they remained stable. It is concluded that the small increase of blood glucose values in the morning is not a major clinical problem in CSII treated diabetic patients.