TORONTO — Insulin is the mainstay of treatments for type 1 diabetes (T1D), but experts say that additional therapies are needed alongside insulin to optimize health in this population.

“Most adults with T1D do not meet glycemic targets,” said Alanna Weisman, MD, PhD, assistant professor of medicine at the University of Toronto in Toronto, during a presentation at the Diabetes Canada and Canadian Society of Endocrinology and Metabolism (CSEM) Professional Conference 2025.

In addition, conditions such as chronic kidney disease and coronary artery disease “are common in individuals with T1D, and we have limited therapies available for these comorbidities,” she said.

Furthermore, overweight and obesity are also becoming increasingly common in individuals with T1D.

Can Type 2 Diabetes (T2D) Treatments Help?

Researchers have looked at several T2D therapies to see if they might also help T1D.

Metformin, for example, “is thought to be an insulin sensitizer,” said Weisman, and “it could help mitigate weight gain associated with insulin.” However, a 2017 randomized clinical trial (RCT), published in The Lancet, found no substantial long-term change in A1c in patients with T1D who took metformin. Additionally, a 2025 RCT published in Nature Communications found that metformin had no impact on insulin resistance in the livers of patients with T1D.

The potential benefits of DPP-4 inhibitors or gliptins for T1D “are specifically for postprandial glycemia,” said Weisman, “and theoretically, there would also be lower insulin requirements.” However, a 2025 meta-analysis published in PLoS One found no significant or sustained A1c reduction in patients with T1D who received a DPP-4 inhibitor, although there was what Weisman called a “modest” benefit in reducing insulin doses.

SGLT2 inhibitors may also have potential benefits in T1D, she noted. These benefits could include “lower insulin requirements or potentially improved glycemia.” Although these drugs have shown kidney and cardiovascular benefits in other patient populations, no studies have reported similar benefits in people with T1D.

A pair of 2018 RCTs published in Diabetes Care found that a low dose of the SGLT2 inhibitor empagliflozin showed “some A1c benefit,” Weisman said, although “it’s not as magnified as for people on the higher doses.” Of note, rates of diabetic ketoacidosis (DKA) were higher in the high-dose groups, “so there may be a role for considering ultralow doses of SGLT2 inhibitors [to] mitigate the concern regarding DKA.”

Even GLP-1 receptor agonists (RAs) — approved for T2D and obesity — may have benefits in T1D, “including lowering insulin requirements, improving glycemia, and weight loss,” said Weisman. There may also be cardiovascular or kidney benefits, she added, although more research is needed.

A 2025 RCT published in Diabetes Care found that patients with T1D treated with the GLP-1 RA tirzepatide saw an 8.8% decrease in weight over 12 weeks, as well as a 0.4% improvement in A1c and a reduction in insulin doses. There was no increase in DKA or severe hypoglycemia.

“GLP-1 and GLP-1/GIP [glucose-dependent insulinotropic polypeptide] receptor agonists show very promising metabolic and weight benefits, with low risk of adverse effects,” said Weisman, adding that upcoming large trials will “hopefully strengthen the evidence in this area.”

Targeting Insulin

Pramlintide is sometimes used as an adjunct therapy to mealtime insulin to help control blood sugar in adults with T1D or T2D. “The potential benefits are mainly regarding postprandial glycemia and potentially some weight loss,” said Weisman. A 2006 RCT published in Diabetes Care found that patients with T1D who took pramlintide saw a 28% reduction in insulin doses at week 29 compared with a 4% reduction in placebo-treated patients. Weight loss in both groups was similar.

However, overall pramlintide has “modest” benefits, she said, and it requires an additional injection at each meal.

Melissa-Rosina Pasqua, MD, PhD, assistant professor of medicine at McGill University in Montreal, said in a separate presentation at the conference that adjunctive therapies for insulin also play a role in improving the health of patients with T1D who are using automated insulin delivery (AID) systems.

AID has had a major impact on T1D care, she said, “but it does not perfect care for either glycemic or nonglycemic targets in T1D. Adjunctive therapies are a [way] to [address] the postprandial concerns in AID and potentially add other benefits that AID does not provide.”

For example, Pasqua pointed to a small crossover study carried out by her group and published in 2022 in Diabetes Care. It looked at the use of empagliflozin alongside an AID. “Overall, the highest time-in-range is when you have AID and empagliflozin,” she said, “so there’s a little bit of synergy there.”

However, more studies looking at the safety and efficacy of these therapies in T1D are needed.

Weisman reported receiving funding or speaker honoraria from Breakthrough T1D, Canadian Institutes of Health Research, CPD Network, Diabetes Canada, Diabetes Care Community, Noble Insights, and Ontario Health. Pasqua reported receiving speaker honoraria from Abbott, Medtronic, and Sanofi.

Shawn Radcliffe is a freelance health and science journalist based in Ontario, with more than 15 years of experience writing about general health, medical research, mental health, and other topics for print and online publications. He previously performed laboratory and clinical research and research administration at universities in Philadelphia and Portland, Oregon. He has a master’s degree in science education from Drexel University.