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Diabetes Spectr. 2019 May;32(2):139-144. doi: 10.2337/ds18-0054.

Duration of Insulin Supply in Type 1 Diabetes: Are 90 Days Better or Worse Than 30 Days?

Author information

1
Department of Internal Medicine, University of Michigan, Ann Arbor, MI.
2
Institute of Healthcare Policy and Innovation, University of Michigan, Ann Arbor, MI.
3
Pediatric Endocrinology, Child Health Evaluation and Research Unit, University of Michigan, Ann Arbor, MI.

Abstract

Objective:

There have been few studies regarding the duration of insulin prescriptions and patient outcomes. This study evaluated whether A1C varied with the duration of insulin prescription in patients with type 1 diabetes.

Methods:

We conducted a longitudinal investigation (from 2001 to 2015) within a nationwide private health insurer. A cohort study was first used to compare A1C after 30-day only, 90-day only, and a combination (30-day and 90-day) of insulin prescriptions. Second, a self-controlled case series was used to compare A1C levels after 30-day versus 90-day prescriptions for the same person.

Results:

In the cohort study, there were 16,725 eligible patients. Mean A1C was 8.33% for patients with 30-day prescriptions compared to 7.69% for those with 90-day prescriptions and 8.05% for those who had a combination of 30- and 90-day prescriptions (P <0.001). Results were similar when stratified by age and sex. Mean A1C was 7.58% when all prescriptions were mailed versus 8.21% when they were not. In the self-controlled case series, there were 1,712 patients who switched between 30- and 90-day prescriptions. Mean A1C was 7.87% after 30-day prescriptions and 7.69% after 90-day prescriptions (P <0.001). Results were similar when stratified by sex. For this within-person comparison, the results remained significant for those ≥20 years of age (n = 1,536, P <0.001), but not for youth (n = 176, P = 0.972).

Conclusion:

There was a statistically significant but clinically modest decrease in A1C with 90-day versus 30-day insulin prescriptions in adults. A mailed 90-day insulin prescription may be a reasonable choice for adults with type 1 diabetes.

PMID:
31168285
PMCID:
PMC6528389
[Available on 2020-05-01]
DOI:
10.2337/ds18-0054

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