Fact-check: Mayo Clinic Proceedings on tirzepatide in type 1 diabetes

What the video covers

Two research fellows at Mayo Clinic Florida present the four findings of their paper on tirzepatide in adults with type 1 diabetes and overweight or obesity: a mean weight loss of 8.5 percent at a median eight months rising to 12 percent at twelve months; about a one percentage-point fall in A1c with more time in range on continuous glucose monitors and no increase in hypoglycaemia; a 31.6 percent reduction in insulin requirement; and a side-effect profile consistent with the pivotal trials, with no diabetic ketoacidosis and four hypoglycaemic events that needed no assistance. They close by saying the data need validation in a larger prospective study.

What it gets right

The presenters describe their own paper, and the figures they quote are the figures in the abstract (PubMed 39601745). They are careful about design: they call it a study rather than a trial, give a median follow-up rather than a fixed endpoint, and say explicitly that prospective validation is needed. They also name the clinical hesitation honestly, which is the fear of hypoglycaemia when an appetite-suppressing drug is added to insulin, and report that insulin doses fell substantially, which is the mechanism by which that risk is managed.

The background point stands up. People with type 1 diabetes are not spared the rise in obesity, and until recently the only adjunct drug with a type 1 indication in the United States was pramlintide.

What it leaves out or overstates

The opening line, that tirzepatide "can be considered a potential treatment option for patients with type 1 diabetes", runs ahead of the evidence and of the label. Mounjaro's prescribing information states that it is not indicated for type 1 diabetes and has not been studied in that population. Zepbound's indications are chronic weight management and obstructive sleep apnoea in adults with obesity; a person with type 1 diabetes who meets those criteria can be prescribed it for those reasons, but this paper does not change any indication.

The design limits are larger than the video's closing sentence conveys. A retrospective chart review from one health system has no control arm, so the weight and A1c changes cannot be separated from other care those patients received, and the population is people whose clinicians chose to prescribe an off-label drug and who returned for follow-up. Adverse events in chart reviews are under-recorded compared with trials. The video gives no sample size and no confidence intervals; readers should take those from the paper before quoting the percentages.

Where to go next

The next two videos in this playlist are with clinicians who ran the tirzepatide trials in type 2 diabetes and obesity. The trial results themselves are digested on FormBlends Research. For label dosing, the four-week step schedule and the contraceptive caution, see the Tirzepatide Hub. FormBlends offers compounded tirzepatide at formblends.com/products/tirzepatide; compounded tirzepatide is not FDA approved, is not interchangeable with Mounjaro or Zepbound, and has no indication of any kind.