How many Canadians stayed on a GLP-1 medicine plus insulin for a year

Why this study matters

Clinical trials show what a medicine can do when people take it as directed. Real life is different. People stop for many reasons: side effects, cost, hassle, or feeling better. This study is one of the few that looked at Canadian prescription records to see how many people actually keep taking a GLP-1 medicine over a year. It is important to be clear about its scope. The people in it had type 2 diabetes and were taking a GLP-1 medicine together with a long-acting (basal) insulin, using two separate injection devices. It is not a study of weight-management prescriptions.

Who was in the study

The study included Canadian adults with type 2 diabetes who were prescribed a GLP-1 receptor agonist and basal insulin at the same time through separate devices. The authors call this a loose-dose combination, as opposed to a single product that combines both medicines. Two groups were analysed. Cohort 1, the primary cohort, included 12,411 people who had no previous experience with the combination when they started. Cohort 2, an exploratory cohort, included 13,498 people regardless of previous experience. The data covered a five-year period. The summary we reviewed does not give ages, which provinces were included, or which GLP-1 medicines were used.

What the researchers did

This was a retrospective cohort study using a Canadian longitudinal prescription database. Retrospective means the researchers looked back at records that already existed rather than enrolling people and following them forward. Cohort means a defined group was tracked over time.

The main outcome was persistence: the proportion of people who were still filling prescriptions for both medicines 12 months after starting, and the average number of days they stayed on the combination. The summary we reviewed does not describe the exact gap in refills that counted as stopping.

What they found

In Cohort 1, the people new to the combination, overall persistence at 12 months was 47% (R32-C133). In Cohort 2, which included everyone regardless of prior experience, persistence was 45%. The authors describe these figures as similar.

The authors describe overall persistence as low, and lower than what earlier studies reported for a GLP-1 medicine alone or basal insulin alone. The summary we reviewed does not give those earlier figures or the average number of days persistent, so we do not report them.

Side effects and people who stopped

Prescription databases do not record why people stop. This study did not measure side effects. The published summary we reviewed does not report a discontinuation rate separately from the persistence figure, and we do not calculate one, because the two are defined differently in this type of study.

What this study does not tell you

• Everyone had type 2 diabetes and was using insulin at the same time. The persistence figure cannot be applied to people using a GLP-1 medicine on its own, or for weight management without diabetes.
• The study does not say why people stopped. Side effects, cost, coverage rules, switching to a different product, or a clinician's decision could all be involved.
• The summary we reviewed does not say which GLP-1 medicines were used, at what doses, or in which provinces.
• Prescription records show what was dispensed, not what was actually taken.
• The data cover a five-year period before the 2021 publication. Availability, coverage, and the products in use may have changed since.
• The summary we reviewed does not state the funding source.

What it means in Canada

This is one of the few Canadian studies of how long people stay on a GLP-1 medicine, but it describes diabetes care, not weight management. It does not say whether any medicine is right for anyone. For information on specific medicines, see semaglutide in Canada and liraglutide in Canada. Coverage rules can affect whether people keep filling prescriptions; see public drug coverage by province. To see how support programs differ, see compare services.

Related reading

Other studies in this library that bear on the same question.

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