How many people stayed on GLP-1 medicines for six months on Medicaid?

Why this study matters

Clinical trials show what a medicine can do when people are supported by a research team and rarely miss a dose. Real life is different. People forget refills, change plans, run into cost or supply problems, or stop because of side effects. This study looked at what happened when a US public insurance program covered semaglutide (Wegovy, Ozempic) and tirzepatide (Zepbound, Mounjaro) for weight management. For Canadian readers, it is a useful picture of how often people keep taking these medicines outside a trial, even though the insurance system is very different from ours.

Who was in the study

The study included 7493 adults enrolled in MassHealth, the Medicaid program in the state of Massachusetts. Medicaid is a US public insurance program for people with lower incomes. All of them started semaglutide (Wegovy) or tirzepatide (Zepbound) for overweight or obesity between July 1, 2024 and December 31, 2024. People with and without diabetes were included. Everyone was continuously enrolled in the program. Follow-up was six months. The summary we reviewed does not report the age range.

What the researchers did

This was a retrospective cohort study using insurance claims. Retrospective means the researchers looked back at records that already existed. A cohort study follows a group of people over time without assigning them to treatments by chance. There was no comparison group and no placebo. Claims data record when a prescription was filled and paid for, but not whether the person actually took the medicine.

The two main outcomes were:

• Persistence: no gap of more than 56 days between prescription fills.
• Adherence: a "proportion of days covered" of at least 80%, meaning the person had medicine on hand for at least 80% of the days in the follow-up period.

A secondary outcome looked at weight change, but only in a subgroup. In this program, people needed prior authorization to keep receiving the medicine after six months, and the renewal paperwork recorded their weight. The researchers used those records to see how many people in that subgroup had lost at least 5% of their starting body weight.

What they found

Among the 7493 members, 60.8% met the persistence definition and 60.1% met the adherence definition at six months (R32-C134). The authors describe these rates as moderate.

Certain groups were less likely to persist and adhere. These were men, people under 40 years old, people with diabetes, and people without weight-related health conditions. The summary we reviewed does not report the size of these differences.

In the subgroup of members with weight records from prior-authorization renewal, 86.5% had lost at least 5% of their body weight at six months. The subgroup included people on tirzepatide, people on semaglutide, and people who had used both. The authors note that this subgroup was made up of highly persistent and adherent members. The summary we reviewed does not report the size of the subgroup or separate results for each medicine.

Side effects and people who stopped

This study measured refill patterns, not side effects. The summary we reviewed does not report why people stopped filling their prescriptions, and it does not report side effects. Because 60.8% were persistent, the rest had a gap of more than 56 days between fills, but the study does not say whether they stopped for good, paused, or switched.

What this study does not tell you

• The weight-loss result comes from a selected subgroup of people who stayed on the medicine and went through renewal, not from all 7493 members. It should not be read as the average result for everyone who started.
• Claims records show fills, not doses taken. The study could not confirm that people used the medicine as prescribed.
• There was no comparison group, so the study cannot say whether persistence would have been different with other medicines or with different support.
• Follow-up was only six months.
• The setting was a US Medicaid program with its own coverage rules and prior-authorization process. Access and cost in Canada are different.
• Our summary is based on the abstract and extracted data. The summary does not state who funded the study.

What it means in Canada

This study shows that in one US public program, 60.8% of people were still filling their prescriptions regularly after six months. Canadian coverage, cost and access rules are different, so the numbers may not transfer. The study does not say why people stopped. For how these medicines are used in Canada, see semaglutide in Canada and tirzepatide in Canada. For what provincial plans pay for, see public drug coverage by province. To look at care options that include follow-up support, see compare services.

Related reading

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

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