Day-to-day variation in glycemic control in type I and type II diabetes mellitus.

In an attempt to assess day-to-day variation in glycemic control, 12 type I and 12 type II diabetic subjects were hospitalized and had plasma glucose sampled frequently on two consecutive days, during which medication, diet, and physical activity were all held constant. In type I subjects, there was no significant day-to-day correlation in overall mean plasma glucose, mean preprandial plasma glucose, mean postprandial plasma glucose, or urinary glucose excretion. In contrast, these measures were all highly correlated in type II subjects. The data suggest that individuals with type I diabetes may not be able to achieve good glycemic control simply by taking the same dose or doses of insulin each day while rigorously attempting to control diet and exercise.