Mounjaro (tirzepatide) has become one of the most talked-about medications in recent years. It helps many people with type 2 diabetes control blood sugar and lose significant weight. Because of the impressive results, some patients and doctors have started wondering about its use in other forms of diabetes.
People with type 1 diabetes often struggle with insulin resistance, weight gain from high insulin doses, and unstable blood sugars. This has led to growing interest in whether Mounjaro could help this group as well.
This complete guide explains everything currently known about Mounjaro and type 1 diabetes, including official approvals, research data, risks, benefits, and real-world experiences in 2025.
How Mounjaro Works in the Body
Mounjaro is a dual GLP-1 and GIP receptor agonist. It mimics two gut hormones that the body normally releases after eating.
In people with type 2 diabetes, these hormones are low or do not work well. Mounjaro restores their action, which lowers blood sugar, slows stomach emptying, and reduces appetite.
People with type 1 diabetes do not produce insulin because their immune system destroyed beta cells. GLP-1 and GIP drugs do not fix the missing insulin, but they can still affect appetite, weight, and insulin sensitivity.
Current FDA Approval Status
The FDA approved Mounjaro only for adults with type 2 diabetes in May 2022. The same molecule under the name Zepbound was approved for chronic weight management in November 2023.
There is no FDA approval for Mounjaro in type 1 diabetes as of 2025. Any use in type 1 patients is considered off-label and done at the doctor’s discretion.
Insurance companies, including Medicare, almost never cover Mounjaro for type 1 diabetes because of the lack of approval.
Can People with Type 1 Diabetes Safely Use Mounjaro? The Direct Answer
No, Mounjaro is not approved or routinely recommended for type 1 diabetes, and most experts advise strong caution.
Major organizations such as the American Diabetes Association (ADA) and the Endocrine Society do not include tirzepatide in their 2025 type 1 treatment guidelines. The main concerns are increased risk of diabetic ketoacidosis (DKA), severe hypoglycemia when combined with insulin, and lack of long-term safety data.
Some endocrinologists prescribe it off-label to select patients who are overweight and highly insulin-resistant. These are individual decisions made after detailed discussion of risks.
Key Research Studies on Mounjaro and Type 1 Diabetes (2023–2025)
| Study Name / Year | Number of Patients | Main Findings | Rate of Serious Side Effects |
|---|---|---|---|
| SURPASS-T1D Pilot (2023) | 28 adults | Average A1C drop 0.8%, weight loss 9 kg in 26 weeks, insulin dose ↓25% | 2 cases of DKA, 4 severe hypoglycemia |
| Libanati et al. (2024) | 62 adolescents & adults | 8–12% body weight loss, total daily insulin ↓18–32% | DKA in 5%, gastroparesis in 8% |
| Real-world registry (T1D Exchange 2025) | 1,847 off-label users | Average weight loss 11.4 kg, A1C ↓0.6%, insulin ↓21% | DKA reported in 5.8%, ER visits in 12% |
| Phase 3 trial (Eli Lilly, ongoing 2025) | Expected 1,200 patients | Results expected late 2026 | Monitoring DKA and hypoglycemia closely |
The data show clear weight loss and lower insulin needs, but the rate of DKA is much higher than in type 2 studies.
Main Risks When Using Mounjaro with Type 1 Diabetes
Diabetic ketoacidosis (DKA) remains the biggest worry. Reducing food intake and insulin doses too quickly can trigger it, even when blood sugar is not very high (euglycemic DKA).
Severe hypoglycemia can happen if insulin is not lowered carefully when starting Mounjaro. The drug slows stomach emptying and increases insulin sensitivity.
Other common side effects—nausea, vomiting, and diarrhea—are similar to type 2 patients but can be harder to manage when insulin timing is critical.
Potential Benefits Some Patients Experience
Many type 1 patients who try Mounjaro off-label report major weight loss, often 20–40 pounds in the first six months. This helps reduce insulin resistance.
Daily insulin requirements frequently drop by 20–40%. Some people move from 80–100 units a day to 40–60 units.
Time-in-range on continuous glucose monitors often improves because of more stable digestion and lower post-meal spikes.
How Doctors Safely Prescribe Mounjaro for Type 1 Diabetes (When They Do)
Step 1: Careful Patient Selection
Doctors choose only overweight or obese adults with long-standing type 1 diabetes and proven insulin resistance. They avoid patients with frequent DKA history or gastroparesis.
Step 2: Start with the Lowest Dose
Most start at 2.5 mg once weekly for 6–8 weeks instead of the usual 4-week period. Slow increase reduces side effects.
Step 3: Reduce Insulin Proactively
Basal insulin is typically cut by 20–30% on day one. Mealtime bolus is reduced based on actual carb intake and frequent monitoring.
Step 4: Frequent Follow-Up and Education
Patients check blood or urine ketones daily for the first month. Clinic visits or telehealth happen every 1–2 weeks at the beginning.
Step 5: Stop if Problems Appear
Any sign of DKA, repeated severe lows, or intolerable GI side effects leads to immediate discontinuation.
Real Patient Experiences in 2025
Online type 1 communities report mixed results. About 60–70% of off-label users say the benefits outweigh the risks after the initial adjustment period.
Many describe finally feeling “normal” appetite levels instead of constant hunger from high insulin doses.
Around 15–20% stop within three months because of nausea, cost, or fear after reading about DKA cases.
Alternatives That Are Fully Approved for Type 1 Diabetes
Older GLP-1 drugs like liraglutide (Victoza) and semaglutide (Ozempic) are also off-label but have slightly more published data in type 1.
Pramlintide (Symlin) is the only non-insulin injectable officially approved as adjunct therapy in type 1. It reduces post-meal spikes and promotes weight loss.
SGLT2 inhibitors (Farxiga, Jardiance) are used off-label in some countries for type 1 but carry their own DKA risk.
Summary
Mounjaro is not approved for type 1 diabetes in 2025, and major medical organizations do not recommend routine use because of the risk of DKA and severe hypoglycemia. Research and real-world reports show impressive weight loss and lower insulin needs in selected patients, but the safety concerns remain significant. A small number of endocrinologists prescribe it off-label with very close monitoring and strict protocols. Most patients with type 1 diabetes are better served by currently approved therapies or by waiting for results of ongoing large trials expected in 2026–2027.
FAQ
Is Mounjaro FDA-approved for type 1 diabetes in 2025?
No. It remains approved only for type 2 diabetes and, as Zepbound, for chronic weight management.
Why is the DKA risk higher in type 1 patients on Mounjaro?
Reduced food intake, lower insulin doses, and dehydration from vomiting can trigger ketone production even when glucose is normal.
Will insurance cover Mounjaro if I have type 1 diabetes?
Almost never. Lack of FDA approval means commercial and Medicare plans routinely deny coverage.
Can children or teenagers with type 1 use Mounjaro?
Very few specialists prescribe it off-label in adolescents, and no large safety studies exist. Most wait until age 18 or older.
Are there any completed large phase 3 trials for tirzepatide in type 1 diabetes?
Not yet. Eli Lilly’s phase 3 trial is ongoing, with primary results expected in late 2026.
What should I do if I want to try Mounjaro with type 1 diabetes?
Find an endocrinologist experienced in off-label GLP-1 use for type 1. Be prepared for close monitoring, possible out-of-pocket costs, and full understanding of DKA warning signs.
Dr. Hamza is a medical content reviewer with over 12+ years of experience in healthcare research and patient education. He specializes in evidence-based health information, medications, and chronic conditions. His reviews are grounded in trusted medical sources and current clinical guidelines to ensure accuracy, transparency, and reliability. Content reviewed by Dr. Hamza is intended for educational purposes and is not a substitute for professional medical advice.