The influence of insulin use on glycemic control: How well do adults follow prescriptions for insulin?

The purposes of this study were to determine the relationship between insulin self-management and glycemic control and to identify patient characteristics associated with better control.

A Department of Veterans Affairs regional database was used to identify patients with diabetes on chronic insulin therapy (n = 6,222) with dose defined as number of units and doses. The rate of insulin use during a 2-year period was calculated using pharmacy data. Regression analyses were used 1) to predict compliance with prescribed insulin regimens using demographic variables, HbA1c levels, and a measure of diabetes management intensity and 2) to predict HbA1c levels using demographic variables and rates of insulin use.

Insulin use was 77.44 +/- 17% of prescribed amounts, including wastage; HbA1c levels were 7.98 +/- 1.66%. Concomitant oral hypoglycemic agent use (84.89 +/- 16%) was higher than insulin use (P < 0.0001) but correlated with insulin use (r = 0.189, P < 0.0001). Ordinary least-squares regression showed that race, HbA1c levels, and intensity of diabetes management were significant predictors of insulin use. Age, race, and insulin use were significant predictors of HbA1c levels.

Adults prescribed a specific insulin regimen averaged using 77% of prescribed doses, demonstrating good intention to follow the prescription. However, HbA1c higher than the recommended level suggested that the rate of insulin use, the prescribed regimen, or both were inadequate to achieve good glycemic control in patients with long-term insulin use.