From the Guidelines
Mounjaro (tirzepatide) should not be used in patients with Type 1 Diabetes Mellitus (T1DM) outside of a clinical trial setting, as its safety and efficacy for this population have not been established in high-quality studies. According to the most recent guidelines, pharmacologic approaches to glycemic treatment in diabetes, published in 2025 1, there is limited evidence to support the use of tirzepatide in patients with T1DM. While retrospective case series have revealed potential benefits on body weight and glycemic metrics with the addition of semaglutide or tirzepatide for individuals with T1DM and obesity, prospective studies are still ongoing.
Some key points to consider when evaluating the potential use of Mounjaro in patients with T1DM include:
- The primary treatment for T1DM is insulin therapy, and any potential use of Mounjaro would need to be carefully considered alongside insulin management.
- Clinical trials have demonstrated modest reductions in A1C and weight loss with other agents, such as pramlintide and liraglutide, but these results may not be generalizable to tirzepatide.
- The use of SGLT2 inhibitors in T1DM has been associated with an increased rate of diabetic ketoacidosis (DKA), highlighting the need for careful consideration of the risks and benefits of any new medication.
In clinical practice, patients with T1DM should consult with their endocrinologist to discuss the latest research and determine the best course of treatment for their individual case, ensuring that any potential use of Mounjaro or other medications is carefully weighed against the need for proper insulin therapy and management of potential risks.
From the Research
Use of Mounjaro (Tirzepatide) in Patients with Type 1 Diabetes Mellitus (T1DM)
- The use of non-insulin pharmacological therapies, including glucagon-like peptide-1 (GLP-1) receptor agonists, as adjuncts to insulin in T1DM has been explored in several studies 2, 3, 4.
- These studies have shown that non-insulin therapies can improve glycemic control and metabolic parameters in patients with T1DM, although the efficacy is often minimal or modest.
- Specifically, the use of GLP-1 receptor agonists, such as tirzepatide, has been shown to improve glycemic control and reduce insulin doses in patients with T1DM 4.
- A recent observational study found that tirzepatide significantly reduced HbA1c and body weight in adults with T1DM, and was relatively safe and well tolerated 5.
- However, it is noted that tirzepatide is currently approved for use in type 2 diabetes, and its use in T1DM is not yet established 6.
- Further research, including randomized controlled trials, is needed to establish the efficacy and safety of tirzepatide in patients with T1DM 5.
Key Findings
- Tirzepatide has been shown to improve glycemic control and reduce body weight in adults with T1DM 5.
- The drug was relatively safe and well tolerated, with only 2 patients discontinuing the medication in the observational study 5.
- The use of non-insulin pharmacological therapies, including GLP-1 receptor agonists, may be beneficial in patients with T1DM who are prone to hypoglycemia or have residual beta-cell function 2, 3.