Is Mounjaro (tirzepatide) recommended for type 1 diabetes?

Mounjaro (Tirzepatide) for Type 1 Diabetes

Mounjaro (tirzepatide) is not currently recommended or FDA-approved for the treatment of type 1 diabetes. Insulin therapy remains the cornerstone and only FDA-approved first-line treatment for type 1 diabetes management 1, 2.

Current Treatment Standards for Type 1 Diabetes

First-Line Treatment

• Multiple daily insulin injections (MDI) or continuous subcutaneous insulin infusion (CSII/insulin pump) are the standard approaches for type 1 diabetes management
• Insulin therapy must be individualized based on:
  • Carbohydrate intake
  • Pre-meal glucose levels
  • Anticipated physical activity

FDA-Approved Adjunctive Therapy

• Pramlintide is the only FDA-approved non-insulin medication for type 1 diabetes
• Provides modest benefits:
  • A1C reductions of 0.3-0.4%
  • Weight loss of approximately 1 kg
  • Requires reduction in prandial insulin dosing to minimize hypoglycemia risk 1, 2

Investigational Agents for Type 1 Diabetes

The American Diabetes Association guidelines note that several agents approved for type 2 diabetes have been studied as adjuncts to insulin in type 1 diabetes:

1. GLP-1 Receptor Agonists (like liraglutide):

   • Small A1C reductions (0.2-0.4%)
   • Weight reduction (2.2-4.9 kg)
   • Increased hypoglycemia rates (20-30%)
   • Higher risk of hyperglycemia with ketosis (2.2 times more likely at higher doses) 1

2. SGLT2 Inhibitors:

   • Improvements in A1C and body weight
   • Associated with increased risk of diabetic ketoacidosis, including euglycemic DKA 1

3. Metformin:

   • Small reductions in weight and lipid levels
   • No significant improvement in A1C 1

Tirzepatide (Mounjaro) and Type 1 Diabetes

Tirzepatide is a dual GIP/GLP-1 receptor agonist currently approved only for type 2 diabetes 3, 4, 5. Recent research has begun exploring its potential use in type 1 diabetes:

• A 2024 retrospective single-center study of 62 overweight/obese adults with type 1 diabetes showed promising results with off-label tirzepatide use 6:
  • 18.5% weight loss (>46 pounds) at 1 year
  • HbA1c reduction of 0.67% at 1 year
  • Decreased insulin requirements
  • No reported severe hypoglycemia or DKA hospitalizations

However, this was a small, retrospective study without the rigor of a randomized controlled trial.

Safety Considerations and Risks

Using medications approved only for type 2 diabetes in type 1 diabetes carries significant risks:

• Increased risk of diabetic ketoacidosis (DKA)
• Risk of euglycemic DKA (ketoacidosis without significant hyperglycemia)
• Inappropriate reduction in insulin dosing
• Gastrointestinal side effects
• Hypoglycemia risk 2

Clinical Decision Algorithm

1. First-line treatment: Optimize insulin therapy (MDI or insulin pump)
2. If additional glycemic control needed: Consider pramlintide (only FDA-approved adjunctive therapy)
3. For overweight/obese patients with type 1 diabetes with poor control despite optimized insulin:
   • Discuss that all non-insulin medications (except pramlintide) are off-label
   • Consider referral to specialized centers with experience in managing complex type 1 diabetes

Important Caveats

• The American Diabetes Association clearly states that adjunctive agents beyond pramlintide are not approved for type 1 diabetes 1
• Strong recommendation for large prospective randomized controlled trials before widespread use of tirzepatide in type 1 diabetes 6
• Discontinuing or significantly reducing insulin when starting adjunctive therapies can lead to poor outcomes and increased DKA risk

While preliminary research on tirzepatide in type 1 diabetes shows promise, particularly for overweight/obese patients, larger clinical trials are needed before it can be recommended as standard treatment.