Assessing insulin effectiveness at the end of the day: Once-daily versus twice-daily insulin glargine injection

Objective: Evidence supporting the twice-daily administration of insulin glargine as an approach to address its waning effectiveness at the end of a 24 hour period is sparse. We hypothesized that insulin concentrations determined during the last four hours of a 24 hour period would be greater when identical doses of insulin glargine were administered twice-daily as compared to once-daily among type 1 diabetes patients. Research Methods: Ten subjects with insulin deficient type 1 diabetes were admitted for two 38-hour studies at least one week apart. Patients received full-dose insulin glargine once daily at 0800 and half-dose insulin glargine twice-daily at 0800 and 2000 for at least one week in random order prior to overnight studies. Overnight glucose was stabilized with intravenous insulin on the evening prior to study, and subjects fasted and did not receive short acting insulin during the study period. Insulin concentrations were assessed every 30 minutes with an ultrasensitive assay between study hours 20 and 24. Results: Insulin concentrations for the final four hours of study period did not differ between once-daily and twice-daily insulin glargine administration (p = 0.38). Home glucose testing results and overnight plasma glucose concentrations did not differ between study conditions. Conclusions: These results demonstrate that insulin concentrations are equivalent during the last four hours of a 24-hour period when insulin glargine is administered once- or twice-daily. These findings do not support a role for twice-daily insulin glargine in the management of patients with type 1 diabetes.