GLP-1 receptor agonists (GLP-1 RAs) have transformed care for people with type 2 diabetes and obesity. These medications reduce blood sugar, lower insulin needs, and promote sustained weight loss. But can they also benefit those with type 1 diabetes (T1DM)?
New evidence suggests GLP-1 RAs may have a role as adjuncts—not replacements—for insulin in people with type 1 diabetes. When used selectively and under expert supervision, they can support better glucose control, help reduce insulin requirements, and assist with weight management.
What Are GLP-1 RAs and How Do They Work?
GLP-1 receptor agonists mimic a gut hormone called glucagon-like peptide-1. In response to meals, this hormone helps regulate blood sugar by:
- Stimulating insulin (only when glucose is elevated)
- Suppressing glucagon (which raises blood sugar)
- Slowing gastric emptying
- Reducing appetite
In people with type 2 diabetes, these actions improve blood sugar control and often lead to weight loss. However, in type 1 diabetes, where the body doesn’t make insulin, these medications do not replace insulin therapy—but they can still help improve metabolic outcomes when added thoughtfully.
ADA 2025: Liraglutide (Victoza & Saxenda) in Focus
The American Diabetes Association’s 2025 Standards of Care now acknowledge the potential use of GLP-1 RAs as an adjunct to insulin in type 1 diabetes[1].
A clinical trial using liraglutide 1.8 mg daily showed:
- A modest A1c reduction of 0.4%
- Average weight loss of 5 kg (11 lbs)
- Reduced total daily insulin doses
These benefits are particularly important for individuals with overweight or obesity, who often face higher insulin resistance. Liraglutide helped preserve C-peptide (a marker of residual beta-cell function) to some degree. However, once the medication was discontinued, the loss of C-peptide accelerated—more so than in the placebo group. This highlights the need for cautious, long-term planning when using these medications in this setting.
Semaglutide (Ozempic) and Tirzepatide (Mounjaro): Real-World Insights
Although not yet FDA-approved for use in type 1 diabetes, semaglutide and tirzepatide have been used off-label in individuals with T1DM and obesity or high insulin requirements. Retrospective case series suggest:
- Significant weight loss
- Improved glucose time-in-range
- Reduced insulin needs
Early results are encouraging, but prospective trials are still ongoing. Until more data become available, use of these agents should be carefully personalized and monitored closely.
What Do Meta-Analyses Tell Us?
Several comprehensive reviews and meta-analyses have examined how GLP-1 RAs perform in type 1 diabetes:
1. Small but Consistent A1c Benefits
- Park et al. reported liraglutide reduced A1c by 0.1%, body weight by 2.2 kg, and insulin use by 4.3 units/day, with some increase in nausea and ketosis risk[2].
- Tan et al. found greater A1c reduction (0.2%) and weight loss (4.0 kg) with a 5.7 unit/day insulin decrease. Importantly, these changes did not increase severe hypoglycemia or diabetic ketoacidosis[3].
2. Glycemic Variability and Monitoring Needs
While A1c is a valuable measure, it doesn’t capture the full picture. Karakasis et al. found that GLP-1 RAs reduced time spent above the target glucose range, suggesting improved day-to-day control. These agents also led to a slight increase in time spent below range, raising the risk of hypoglycemia[4].
This highlights the need for careful insulin adjustment, continuous glucose monitoring (CGM), and personalized follow-up when initiating GLP-1 therapy in type 1 diabetes. The benefits of improved glucose stability must always be balanced against the risk of low blood sugars.
3. Effects Beyond Diabetes
GLP-1 RAs offer benefits that extend beyond blood glucose control. Several studies (Rivera at al) report modest reductions in systolic and diastolic blood pressure, which may support cardiovascular and kidney health—especially important in people with metabolic syndrome or early diabetic kidney disease[5].
In addition, these medications promote weight loss, improve insulin sensitivity, and may lower inflammatory markers, contributing to a healthier overall metabolic profile. These broader effects support their use in a more holistic, individualized approach to managing type 1 diabetes.
| Study / Source | GLP-1 RA Used | A1c Change (%) | Weight Loss (kg) | Insulin Dose Change (IU/day) | Notable Effects / Considerations |
|---|---|---|---|---|---|
| ADA 2025 Guidelines | Liraglutide 1.8 mg | ↓ 0.4% | ↓ 5.0 | ↓ (not specified) | No C-peptide preservation; benefits reversed after stopping |
| Park et al. Meta-analysis | Liraglutide | ↓ 0.1% | ↓ 2.2 | ↓ 4.3 | Higher nausea and ketosis risk |
| Tan et al. Meta-analysis | Liraglutide, Exenatide | ↓ 0.2% | ↓ 4.0 | ↓ 5.7 | No increase in DKA or severe hypoglycemia |
| Karakasis et al. | Multiple GLP-1 RAs | ↓ (not specified) | ↓ (not specified) | ↓ (not specified) | Less time above range, more time below target |
| Case Series Reports | Semaglutide, Tirzepatide | ↓ (variable) | ↓ (variable) | ↓ (variable) | Encouraging real-world results; trials ongoing |
Why It Works: Beyond the A1c
GLP-1 RAs do more than lower blood sugar. As Harris and Boland emphasized, these agents reduce post-meal glucose spikes by suppressing glucagon, which is often inappropriately elevated in T1DM. This can help blunt the sharp rises in blood sugar seen after meals, especially in individuals struggling with postprandial control[6].
They also promote earlier satiety, curb cravings, and slow food absorption. All of these effects can help lower overall insulin needs, improve weight management, and possibly reduce glucose variability—a key challenge in type 1 diabetes.
What Are the Risks?
Common side effects include:
- Nausea
- Vomiting
- Diarrhea or constipation
- Fatigue or appetite loss
These are usually dose-dependent and tend to improve over time. A small risk of ketosis has been noted, particularly if insulin doses are reduced too quickly. No significant increase in severe hypoglycemia has been observed across major trials, but low blood sugars can still occur if insulin adjustments aren’t made carefully.
The Takeaway: A Personalized, Holistic Approach
GLP-1 RAs are not a replacement for insulin in type 1 diabetes. But for selected patients—especially those with obesity, high insulin needs, or glucose variability—they can be powerful adjuncts.
Their benefits include:
- Modest A1c improvement
- Significant weight loss
- Lower insulin requirements
- Reduced blood pressure and improved metabolic flexibility
Yet these advantages must be weighed against potential gastrointestinal side effects, the risk of hypoglycemia, and the need for frequent monitoring and individualized care.
In expert hands, with a holistic, multi-angle approach, GLP-1 RAs can improve quality of life and metabolic outcomes in carefully selected individuals with type 1 diabetes.
For patients interested in this therapy, a conversation with an endocrinologist or diabetes specialist is the best first step.
References:
- Diabetes Care. 2025;48(Supplement_1):S181-S206. doi:10.2337/dc25-S009. 9. Pharmacologic Approaches to Glycemic Treatment: Standards of Care in Diabetes-2025
- Park J, Ntelis S, Yunasan E, et al. The Journal of Clinical Endocrinology and Metabolism. 2023;109(1):279-292. doi:10.1210/clinem/dgad471. Glucagon-Like Peptide 1 Analogues as Adjunctive Therapy for Patients With Type 1 Diabetes: An Updated Systematic Review and Meta-Analysis.
- Tan X, Pan X, Wu X, et al. Frontiers in Pharmacology. 2023;14:975880. doi:10.3389/fphar.2023.975880. Glucagon-Like Peptide-1 Receptor Agonists as Add-on Therapy to Insulin for Type 1 Diabetes Mellitus.
- Karakasis P, Koufakis T, Patoulias D, et al. Diabetes, Obesity & Metabolism. 2024;26(12):6043-6054. doi:10.1111/dom.15979. Effects of Glucagon-Like Peptide-1 Receptor Agonists on Glycated Haemoglobin and Continuous Glucose Monitoring Metrics as Adjunctive Therapy to Insulin in Adults With Type 1 Diabetes: A Meta-Analysis of Randomized Controlled Trials.
- Rivera FB, Lumbang GNO, Gaid DRM, et al. Diabetes, Obesity & Metabolism. 2024;26(6):2209-2228. doi:10.1111/dom.15529. Glucagon-Like Peptide-1 Receptor Agonists Modestly Reduced Blood Pressure Among Patients With and Without Diabetes Mellitus: A Meta-Analysis and Meta-Regression.
- Harris KB, Boland CL. Pharmacotherapy. 2016;36(9):1011-20. doi:10.1002/phar.1804. Adjunctive Role of Glucagon-Like Peptide-1 Receptor Agonists in the Management of Type 1 Diabetes Mellitus.
About Dr. Gerti Tashko, MD
Dr. Gerti Tashko, MD, is a board-certified endocrinologist based in Montgomery County, Maryland. He is uniquely certified in endocrinology, lipidology, hypertension, and obesity medicine. His practice offers comprehensive, root-cause-focused metabolic and endocrine care, available both virtually and in person. He uses advanced diagnostics, personalized nutrition, and preventive medicine to optimize long-term health outcomes.
