Background:  Many factors contribute to the need for prandial insulin in Type 1 diabetes. However, patients’ success in achieving normal postprandial glucose concentration is understudied. The aim of the present study was to determine how often patients with Type 1 diabetes achieve normal postprandial glucose concentrations and to evaluate factors associated with postprandial hypo‐ and hyperglycemia.

Methods:  Data on food intake, physical activity, insulin administration, and blood glucose concentration were collected using a self‐administered questionnaire from 331 patients with Type 1 diabetes (43% men; mean age 49 ± 12 years; mean diabetes duration 32 ± 13 years). Of these, 179 provided data on blood glucose concentrations measured 110–150 min postprandially. One such meal per patient was randomized for analyses.

Results:  Hypoglycemia (<4.0 mmol/L), normoglycemia (4.0–7.9 mmol/L), and hyperglycemia (≥8.0 mmol/L) were observed after 23%, 36%, and 41% of meals, respectively. The three postprandial glycemia groups did not differ with respect to the meal composition or the timing of the postprandial blood glucose measurement. In women, postprandial hyperglycemia was associated with shorter diabetes duration and higher preprandial blood glucose concentration, whereas postprandial hypoglycemia was associated with higher physical activity. No single factor explained the postprandial glycemic state in men.

Conclusions:  A total of 64% of patients estimated their prandial insulin need inappropriately, suggesting that estimation of the optimal prandial insulin dose is not easy, even after a long duration of diabetes.