Dawn phenomenon and Somogyi effect in IDDM.

We examined the clinical relevance of a rise in fasting blood glucose (BG) between 0300 and 0600 in 97 patients with insulin-dependent diabetes mellitus (IDDM) receiving sequentially conventional (CT) and basal-bolus (BBIT) insulin therapies and assessed the impact of one potential causal factor, i.e., posthypoglycemic hyperglycemia, with 231 BG profiles (97 during CT, 134 during BBIT) in which BG was measured every 3 h over a 24-h period. A rise in BG between 0300 and 0600 occurred in 157 of 231 (68%) profiles. The mean magnitude of this rise was 56 +/- 39 mg/dl and was lower (P less than .05) during BBIT (48 +/- 35 mg/dl, n = 97) than CT (62 +/- 43 mg/dl, n = 97). A dawn rise (between 0300 and 0600) greater than 50 mg/dl occurred in 40 of 97 (41%) profiles during CT and 26 of 97 (27%) during BBIT (P less than .05). When all profiles were grouped according to the magnitude of this rise in BG, the mean daytime BG (from 0900 to 1800) was higher (P less than .05) after an 0300-0600 BG rise greater than 50 mg/dl compared with groups of profiles showing either a fall in BG or a rise less than 50 mg/dl; a rise in BG between 0300 and 0600 correlated (r = .38, P less than .0001) with the subsequent mean daytime BG. Nocturnal hypoglycemia (BG less than 60 mg/dl) recorded at 2400 and/or 0300 occurred in 57 of 231 (25%) profiles.(ABSTRACT TRUNCATED AT 250 WORDS)