What is glucagon-like peptide-1?
Glucagon-like peptide-1 (GLP-1) is a hormone that’s released from the intestines after eating. It signals to the pancreas to release insulin.
In people with T1D, the levels of GLP-1 hormones are typically normal, but the body doesn’t respond well to it.
GLP-1 receptor agonists are medications that mimic the natural GLP-1 hormone. Taking these medications allows the pancreas to respond better to GLP-1.
How do GLP-1 therapies work?
GLP-1 hormones help manage blood glucose levels by:
- suppressing the release of glucagon (a hormone that raises blood glucose levels)
- slowing how fast the stomach empties
- increasing feelings of fullness.
GLP-1 therapies are usually injected, but oral versions are available. The drug is taken daily or weekly depending on the specific medication. The benefits of the medication are only present while taking them continuously, so these drugs are intended for long-term management.
GLP-1 therapies have been shown to reduce the risk of long-term cardiovascular complications in people with type 2 diabetes, such as heart attack and stroke. Research is needed to determine the efficacy of how they impact cardiovascular complications in T1D.
What are GLP-1 therapy medications?
Examples of GLP-1 therapies include:
- Semaglutide (Brand names: Ozempic and Wegovy)
- Dulaglutide – (Brand name: Trulicity)
- Liraglutide – (Brand name: Victoza)
- Tirzepatide* – (Brand name: Mounjaro)
*Tirzepatide is a GLP-1 receptor agonist that also promotes the activity of glucose-dependent insulinotropic polypeptide. This is a hormone that helps stimulate insulin release after eating.
Are GLP-1 therapies safe for people with type 1 diabetes?
In the past, GLP-1 therapies haven’t been considered safe for people with type 1 diabetes (T1D) because they could cause serious side effects like severe hypoglycaemia and diabetic ketoacidosis (DKA). But these trials were done with older GLP-1 drugs, and we now have much improved versions that don’t cause such serious side effects.
Technology to help people manage T1D has also advanced drastically since then, and we know have devices like continuous glucose monitors and automated insulin delivery systems to mitigate risks.
A consensus review published in 2025 concluded that GLP-1 therapies have the potential to improve blood glucose management in people with T1D without increasing their risk of severe hypoglycaemia or DKA. The report recommended further clinical trials of GLP-1 therapies and set out guidance for using these medications safely alongside insulin to treat T1D.
Benefits of GLP-1 therapies for people with T1D
Evidence from clinical trials and real-world off-label use (where clinicians use their judgement to prescribe GLP-1 therapies, even though they aren’t approved) in people with T1D has demonstrated that GLP-1 medications can:
- lower HbA1c
- increase time-in-range
- reduce the amount of daily insulin needed
- assist with weight loss.
Clinical trials of GLP-1 therapies
Breakthrough T1D is funding clinical trials of GLP-1 therapies around the world including in the US, UK, the Netherlands and Kuwait. The following clinical trials are funded by Breakthrough T1D in Australia.
- The RESET1 study (REducing Cardiometabolic Risk with SEmaglutide in Type 1 diabetes) is testing whether semaglutide can improve heart health in people with T1D in Sydney.
- The TIRTLE1 (Tirzepatide in Adults with Type 1 Diabetes) clinical trial tested whether a once-weekly injection of tirzepatide is safe and beneficial for people living with T1D. The results showed that tirzepatide can safely decrease the amount of insulin people with T1D need to take, helping them to stay within a healthy blood glucose range.
- The TIRTLE2 clinical study is now exploring in more depth how tirzepatide works in people with T1D, and whether it affects how sensitive people are to insulin.
Dr Jennifer Snaith is leading these clinical trials, and we fund her research through a Fellowship. This supports her career development and gives her dedicated time to conduct her research alongside her work with patients.
Pharmaceutical companies are also funding research in this area. For example, Eli Lilly is running clinical trials of tirzepatide, which is a crucial step towards regulatory approval for the drug.