Dawn phenomenon: its frequency in non-insulin-dependent diabetic patients on conventional therapy.

The frequency of the dawn phenomenon has been studied in non-insulin-dependent diabetic (NIDDM) patients while they continued with their conventional therapy. Plasma glucose (PG) and immunoreactive insulin (IRI) were estimated hourly from 0300 to 0900 h in 19 NIDDM patients; 9 patients were treated by diet alone (group 1), and 10 patients were treated by diet and oral hypoglycemic agents (group 2). The dawn rise of plasma glucose was demonstrated in 17 (89.5%) of the 19 patients with mean +/- SE plasma glucose at 0300 h of 7.0 +/- 0.5 mM and at 0800 h of 8.4 +/- 0.6 (P less than .01). IRI in all patients rose from 14.7 +/- 1.3 microU/ml at 0500 h to 18.1 +/- 1.8 microU/ml at 0700 h (P less than .05). The changes in IRI levels at any time from 0300 to 0800 h in groups 1 and 2 when considered separately were insignificant. Thus, the dawn phenomenon occurs commonly in NIDDM patients taking their conventional therapy.