Adding Liraglutide to Insulin in Type 1 Diabetes: What 5 Trials Show | Research

The takeaway

Liraglutide added to insulin in type 1 diabetes produced meaningful weight loss and reduced insulin needs, but only modestly improved blood sugar and substantially increased nausea.

-4.87 kg weight loss
Liraglutide 1.8 mg produced significant weight reduction in type 1 diabetes patients already on insulin

What the researchers found

Across 5 RCTs with 2,445 participants, liraglutide added to insulin in type 1 diabetes produced modest HbA1c reductions (up to -0.24% with 1.8 mg dose), significant weight loss (up to 4.87 kg), and decreased total daily insulin requirements — mainly bolus insulin.

Severe hypoglycemia was non-significantly reduced (OR=0.80), but gastrointestinal side effects increased substantially: nausea odds were 4.7 times higher and vomiting 2.5 times higher. Heart rate also increased. No link to diabetic ketoacidosis or malignancies was found.

Why it matters

Type 1 diabetes treatment has relied almost exclusively on insulin, with limited options for adjunct therapy. GLP-1 agonists like liraglutide are widely used in type 2 diabetes but their role in type 1 is less established. This meta-analysis provides the most comprehensive evidence to date that liraglutide can meaningfully reduce weight and insulin requirements in T1D patients, though the blood sugar benefit is modest and GI side effects are significant.

The numbers in context

n=2,445 across 5 RCTs · HbA1c: -0.24% (1.8 mg) · Weight loss: -4.87 kg (1.8 mg) · Nausea OR=4.70 · Vomiting OR=2.50 · Severe hypoglycemia OR=0.80 (NS)

How the study worked

Systematic review and meta-analysis of 5 randomized controlled trials (≥12 weeks duration) comparing liraglutide vs placebo as add-on to insulin in type 1 diabetes patients. Searched major databases and grey literature through October 2018. Reported per PRISMA guidelines. Assessed efficacy (HbA1c, weight, insulin dose) and safety (hypoglycemia, GI events, ketoacidosis) endpoints.

Who was studied

Adults with type 1 diabetes using insulin therapy

What this study cannot tell us

Only 5 trials met inclusion criteria, limiting the ability to detect rarer adverse events. Follow-up durations were relatively short (≥12 weeks), so long-term safety and efficacy in T1D remain uncertain. The modest HbA1c reduction (-0.24%) may not justify the high rate of GI side effects for all patients. Individual patient factors that predict who benefits most were not explored.

How to read the evidence

This is a systematic review and meta-analysis of 5 randomized controlled trials — among the highest levels of clinical evidence. The consistent results across trials (I²=0% for key outcomes) strengthen confidence in the findings.

When this study was published

Published in 2020 using data through October 2018. The findings remain relevant as liraglutide is still not FDA-approved for T1D, and newer GLP-1 drugs are now being studied in this population.

The bigger picture

While GLP-1 agonists have transformed type 2 diabetes and obesity treatment, their role in type 1 diabetes remains niche. This meta-analysis suggests liraglutide's main benefit in T1D is weight loss and insulin-sparing rather than blood sugar control — a different value proposition than in T2D. The FDA has not approved any GLP-1 for T1D, and the high GI side effect burden makes patient selection important.

Questions still open

Could newer GLP-1 agonists like semaglutide offer better glycemic control in T1D with fewer side effects?
Which T1D patients benefit most — those who are overweight, those with high insulin requirements, or both?
Would longer trials reveal additional safety concerns or show that GI side effects diminish over time?

Common questions

Is liraglutide approved for type 1 diabetes?

No. Liraglutide is FDA-approved for type 2 diabetes (as Victoza) and obesity (as Saxenda), but not for type 1 diabetes. Some doctors prescribe it off-label for T1D patients who need help with weight or insulin dose reduction, but this is not standard practice.

Why was the blood sugar improvement so small?

In type 1 diabetes, the body produces essentially no insulin, so blood sugar control depends entirely on injected insulin. Liraglutide works partly by enhancing insulin release, which isn't possible in T1D. Its benefits here come mainly from slowing digestion and reducing appetite, which helps with weight but has limited impact on HbA1c.

Read the original research

Liraglutide as Adjunct to Insulin Treatment in Patients with Type 1 Diabetes: A Systematic Review and Meta-analysis.

Current diabetes reviews, 16(4), 313-326

View on PubMed ↗Publisher’s paper ↗

Citation

Dimitrios, Patoulias; Michael, Doumas; Vasilios, Kotsis; Konstantinos, Stavropoulos; Konstantinos, Imprialos; Ioanna, Zografou; Konstantinos, Petidis; Spyridon, Bakatselos; Asterios, Karagiannis. (2020). Liraglutide as Adjunct to Insulin Treatment in Patients with Type 1 Diabetes: A Systematic Review and Meta-analysis.. Current diabetes reviews, 16(4), 313-326. https://doi.org/10.2174/1573399815666190614141918