Insulin wastage in ambulant practice.

The total insulin consumption in 162 insulin-requiring diabetic patients was calculated from the prescriptions of purchased insulin for 1979-80. The mean daily consumption was 58.6 U, whereas the actual dose injected was 41.7 U. A mean of 1.9 doses was injected daily, which yields a loss per dose of 8.9 U (SD +/- 7.9). The dose loss was independent of age and sex and only marginally dependent on insulin dose. Visual impairment increased the loss. From a direct study of 101 patients while drawing their usual morning dose of insulin into the syringe, the following major factors underlying insulin wastage emerged: (1) expulsion of surplus insulin into the air instead of into the vial, when adjustment of the insulin dose is made; (2) use of syringes with a separate needle instead of new low-dead-space syringes; and (3) unnecessary use of 2-ml syringes for doses of insulin less than or equal to 40 U (less than or equal to 1 ml).