GLP-1s in type 1 diabetes: the first expert recommendations

Why people with type 1 are using GLP-1 drugs

Type 1 diabetes is caused by loss of the insulin-producing cells, so insulin is the core treatment. But many people with type 1 also have overweight or obesity and rising cardiovascular risk, and GLP-1 drugs, which lower appetite and weight, are attractive. They are approved for type 2 diabetes and obesity, not for type 1. The Diabetes Technology Society's consensus notes the growing interest in using GLP-1 drugs in type 1 despite their not being approved by FDA for it, in the absence of randomised trials documenting efficacy and safety in this group (consensus report) ¹.

The labels reflect that gap. The Wegovy label states that its use in patients with type 1 diabetes or in combination with insulin has not been evaluated, while warning that combining it with insulin may increase the risk of hypoglycaemia, including severe hypoglycaemia ².

The first expert consensus

The Diabetes Technology Society convened three consensus meetings in 2024 of clinicians and researchers in diabetes technology, GLP-1 therapy and type 1 diabetes, focused on adults with type 1 who use automated insulin delivery (AID), the 'closed-loop' systems that adjust insulin from a continuous glucose monitor. The panel voted in favour of 31 recommendations and concluded that, in these adults, GLP-1 drugs have the potential to provide effective adjunct therapy and to improve glucose and metabolic outcomes without increasing the risk of severe hypoglycaemia or diabetic ketoacidosis (consensus report, published in the 2025 volume) ¹.

Two points about it matter. It is a consensus of expert opinion, not a trial, written because trials were lacking. And several panel members disclosed research support or advisory roles with companies including Novo Nordisk and Lilly, which make GLP-1 drugs, as well as insulin-pump and sensor makers ¹. Neither point invalidates it, but both are worth knowing.

The first big trials: liraglutide in ADJUNCT ONE and TWO

The largest trials are older and used liraglutide. In ADJUNCT ONE, 1,398 adults with type 1 were randomised to liraglutide at one of three doses or placebo, added to treat-to-target insulin for 52 weeks. HbA1c fell slightly more with the higher doses, by 0.20 percentage points more than placebo at 1.8 mg, and insulin doses and body weight fell too (randomised trial) ³.

ADJUNCT TWO, with 835 adults on capped insulin doses for 26 weeks, found similar modest HbA1c reductions and weight loss of up to 5.1 kg, with improved quality of life. It also found the risks that worry clinicians: more symptomatic hypoglycaemia with liraglutide 1.2 mg than placebo (21.3 against 16.6 events per patient-year) and more episodes of high glucose with ketosis with 1.8 mg (0.5 against 0.1 events per patient-year) (randomised trial) ⁴. A 2023 meta-analysis of 24 studies and 3,377 patients found liraglutide had the most evidence, with effects on HbA1c, weight and insulin dose that grew with the dose (meta-analysis) ⁵.

Semaglutide with automated insulin delivery

Newer trials pair semaglutide with AID systems, the setting the consensus addresses. In a double-blind crossover trial of 28 adults, semaglutide increased time spent in the target glucose range by 4.8 percentage points compared with placebo (randomised crossover trial) ⁶.

ADJUST-T1D randomised 72 adults with type 1 and obesity using AID to weekly semaglutide up to 1 mg or placebo for 26 weeks. The combined goal, more than 70% of time in range, less than 4% time below range and at least 5% weight loss, was met by 36% on semaglutide and none on placebo. HbA1c was 0.3 points lower, time in range 8.8 points higher and weight 8.8 kg lower. There were two severe hypoglycaemia events in each group and no diabetic ketoacidosis (randomised trial, funded by Breakthrough T1D) ⁷.

Tirzepatide and real-world use

Tirzepatide has no randomised trial in type 1 in what we read. A 2026 real-world study of 250 people with type 1 and a BMI of 27 or more found that over 12 months tirzepatide gave the greatest weight loss (10.9%), followed by semaglutide and liraglutide, with modest HbA1c reductions (0.65, 0.33 and 0.23 points), and no severe hypoglycaemia or ketoacidosis was reported (observational study) ⁸. Observational data cannot rule out that the people chosen for each drug differed.

The risks: low blood sugar, ketones and insulin doses

Three risks dominate. Low blood sugar: GLP-1 drugs lower glucose and reduce appetite, so insulin needs fall, and if insulin is not reduced, hypoglycaemia can follow; ADJUNCT TWO found more symptomatic hypoglycaemia at one dose ⁴, and the Wegovy label warns of severe hypoglycaemia with insulin ². Ketones: in type 1, cutting insulin too far, or eating much less, can push the body towards ketosis; ADJUNCT TWO found more high glucose with ketosis at the top dose ⁴. The newer AID trials did not see diabetic ketoacidosis ⁷, and the consensus judged the risk not increased in AID users ¹, but the trials were small.

Insulin adjustment is therefore the practical heart of it. Automated systems adapt to some degree, which is part of why the consensus focused on AID users. Anyone using injections rather than AID needs closer guidance, and anyone using a GLP-1 drug should know how to check ketones and when to seek help. Our guide to peptides and blood sugar explains the interaction in general terms.

How much insulin changes

A post hoc analysis of ADJUST-T1D quantified the insulin change. Over 26 weeks, total daily insulin fell 22.6% with semaglutide compared with placebo, driven more by reductions in mealtime (bolus) insulin, which fell 30.5%, than by background (basal) insulin (secondary analysis) ⁹. That is a large shift for anyone dosing by injection, and it is one reason the consensus centred on automated systems that adjust insulin in real time ¹.

What happens when people stop

Benefits fade when the drug is stopped. In the 12 weeks after ADJUST-T1D ended, the 22 participants who had been on semaglutide and stopped saw a larger fall in time in range than those who had been on placebo (a median change of -3.6 against +1.5 percentage points) (follow-up analysis) ¹⁰. Anyone starting a GLP-1 drug in type 1 should plan with their team for how insulin will be readjusted if they stop, whether by choice, side effects or a supply problem.

What reviews of all the evidence say

A 2026 umbrella review that pooled systematic reviews, meta-analyses and genetic studies found GLP-1 drugs in type 1 gave clinically meaningful weight loss of about 4 to 5 kg and lower insulin doses, statistically significant but modest HbA1c reductions of 0.2 to 0.3 points, and no improvement in time in range across the older studies. Severe hypoglycaemia was not increased, but time below range and gastrointestinal side effects were more frequent, and evidence on ketoacidosis was inconsistent across studies (umbrella review) ¹¹. The newer automated-delivery trials look better than that average, which is consistent with the consensus's focus, but they are small. The review also notes that direct cardiovascular benefits in type 1 remain unproven without dedicated outcome trials ¹¹, which matters because heart protection is one of the main reasons people with type 1 are interested in these drugs.

Off-label prescribing and access

Because no GLP-1 drug is approved for type 1, prescribing is off-label, and insurers may decline to cover it unless another approved indication applies, such as obesity. That leads some people towards compounded or research products. Those carry their own problems, which our guide to compounded and research tirzepatide covers; for someone with type 1, uncertain potency adds unpredictability to insulin dosing that the trials did not face. Our semaglutide brands guide explains which approved product is which.

Questions to ask your diabetes team

• Do I have a reason, such as obesity, that makes a GLP-1 drug worth trying, and is it covered for that use?
• How should my insulin doses change when I start, and who will adjust them?
• Does my AID system or injection regimen affect the risk?
• How and when should I check ketones, and what should I do if they are raised?
• What should make me stop the drug and call you?

The bottom line

GLP-1 drugs are not approved for type 1 diabetes, but evidence is building. The first expert consensus concluded they may help adults who use automated insulin delivery, and trials show modest glucose benefits and meaningful weight loss, with no ketoacidosis in the newest small studies. An older trial found more low blood sugar and ketosis at some doses. This is a treatment to start with a diabetes team, insulin plan in hand, not alone.

Frequently asked questions

Can people with type 1 diabetes take Ozempic?

No GLP-1 drug is approved for type 1 diabetes, so use is off-label. Trials and an expert consensus suggest benefits alongside automated insulin delivery, with careful insulin adjustment.

Do GLP-1 drugs cause DKA in type 1 diabetes?

The ADJUNCT TWO trial found more high glucose with ketosis at liraglutide 1.8 mg. Newer small semaglutide trials with automated insulin delivery found no DKA, and the consensus judged the risk not increased in that setting.

How much weight do people with type 1 lose on semaglutide?

In ADJUST-T1D, adults with obesity on automated insulin delivery lost 8.8 kg more with semaglutide than placebo over 26 weeks.

Is tirzepatide used in type 1 diabetes?

Off-label. A 2026 real-world study found 10.9% weight loss over 12 months; no randomised trial in type 1 was found.

What did the expert consensus recommend?

The Diabetes Technology Society panel voted in favour of 31 recommendations and concluded GLP-1 drugs may provide effective adjunct therapy for adults with type 1 using automated insulin delivery.

Related on Grey Peptides

• Semaglutide
• Peptides and blood sugar
• Semaglutide brands explained

Sources

1. Shah, V. N., et al. (2025). Consensus Report on Glucagon-Like Peptide-1 Receptor Agonists as Adjunctive Treatment for Individuals With Type 1 Diabetes Using an Automated Insulin Delivery System. J Diabetes Sci Technol, 19(1), 191-216. PMID: 39517127
2. Novo Nordisk. WEGOVY (semaglutide) US prescribing information, Warnings and Precautions 5.4. DailyMed version 19, effective June 18, 2026; read October 3, 2026.
3. Mathieu, C., et al. (2016). Efficacy and Safety of Liraglutide Added to Insulin Treatment in Type 1 Diabetes: The ADJUNCT ONE Treat-To-Target Randomized Trial. Diabetes Care, 39(10), 1702-10. PMID: 27506222
4. Ahrén, B., et al. (2016). Efficacy and Safety of Liraglutide Added to Capped Insulin Treatment in Subjects With Type 1 Diabetes: The ADJUNCT TWO Randomized Trial. Diabetes Care, 39(10), 1693-701. PMID: 27493132
5. Park, J., et al. (2023). Glucagon-Like Peptide 1 Analogues as Adjunctive Therapy for Patients With Type 1 Diabetes: An Updated Systematic Review and Meta-analysis. J Clin Endocrinol Metab, 109(1), 279-292. PMID: 37561012
6. Pasqua, M. R., et al. (2025). Subcutaneous weekly semaglutide with automated insulin delivery in type 1 diabetes: a double-blind, randomized, crossover trial. Nat Med, 31(4), 1239-1245. PMID: 39794615
7. Shah, V. N., et al. (2025). Semaglutide in Adults with Type 1 Diabetes and Obesity. NEJM Evid, 4(8), EVIDoa2500173. PMID: 40550013
8. Al Ozairi, E., et al. (2026). Weight loss in people with type 1 diabetes over 12 months: Real-world data comparing tirzepatide, semaglutide and liraglutide. Diabetes Obes Metab, 28(1), 166-173. PMID: 41048008
9. Karakus, K. E., et al. (2026). Effect of Semaglutide on Insulin Dose Reduction in Adults With Type 1 Diabetes and Obesity Using Automated Insulin Delivery Systems: ADJUST-T1D Post Hoc Analysis. Diabetes Care, 49(5), 718-723. PMID: 41429002
10. Montaser, E., et al. (2026). Glycaemic Changes After Semaglutide Discontinuation in Adults With Type 1 Diabetes Using Automated Insulin Delivery: Analysis of the ADJUST-T1D Extension Study. Diabetes Obes Metab, . PMID: 42675550
11. Wójcik-Sosnowska, E., et al. (2026). Metabolic Benefits vs. Cardiovascular Uncertainty: A Critical Review of GLP-1 Receptor Agonists in Type 1 Diabetes. Int J Mol Sci, 27(9). PMID: 42123472

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.