GLP-1 Microdosing and Type 1 Diabetes: What the Adjunct Trials Show About Weight, Insulin Doses, and Hypoglycemia

Type 1 diabetes is an insulin problem, so it is fair to ask why a GLP-1 medicine would have any role. The short answer is weight and post-meal swings. Many adults with type 1 now live with overweight or obesity, and insulin itself makes weight loss harder. A drug that slows the stomach and quiets appetite looks attractive on paper.

This article covers what that looks like in actual studies. It walks through the large liraglutide trials, which tested a dose as low as 0.6 mg, the newer semaglutide and tirzepatide data in people using insulin pumps, and the two safety signals that keep coming up: low blood sugar and ketosis. None of these drugs is approved for type 1 diabetes, and none of the studies tested a microdose protocol as such.

Is GLP-1 microdosing used in type 1 diabetes?

GLP-1 medicines are used in type 1 diabetes only as an add-on to insulin, and only off-label. No trial has tested a microdose protocol in type 1 diabetes. What exists are adjunct trials that used standard titration doses, plus one large trial that included a deliberately low dose.

The status question is settled plainly in the literature. Shah and colleagues opened their 2025 ADJUST-T1D paper in NEJM Evidence with the line "The efficacy and safety of semaglutide in adults with type 1 diabetes are not established." A 2026 tirzepatide study by Akturk and colleagues described its own use as off-label adjunctive treatment.

The mechanics are different from type 2 diabetes. A person with type 1 makes little or no insulin, so a GLP-1 drug cannot lean on the pancreas the way it does in type 2. Its effects come mostly from slower stomach emptying, less appetite and lower glucagon after meals. That changes how much insulin someone needs, which is where both the benefits and the risks begin. Our explainer on insulin sensitivity and blood sugar covers the type 2 side of that story.

What did the lowest dose do in the ADJUNCT ONE trial?

The lowest dose in ADJUNCT ONE, liraglutide 0.6 mg a day, reduced weight but barely touched glucose control. That makes it the closest thing to a microdose data point in type 1 diabetes. Mathieu and colleagues reported the trial in Diabetes Care in 2016: 1,398 adults, randomized 3:1 to liraglutide 1.8, 1.2 or 0.6 mg or placebo, for 52 weeks on top of treat-to-target insulin.

Weight followed the dose closely: 2.2 kg at 0.6 mg, 3.6 kg at 1.2 mg and 4.9 kg at 1.8 mg, all versus placebo. HbA1c told a different story. From a starting average of 8.2%, the treatment differences were -0.20% at 1.8 mg and -0.15% at 1.2 mg, while the -0.09% at 0.6 mg was not statistically different from placebo.

Insulin dose followed the same split. The ratio of insulin used versus placebo was 0.92 at 1.8 mg and 0.95 at 1.2 mg, but 1.00 at 0.6 mg, meaning no change at all. So in type 1 diabetes, a low dose produced a modest weight effect without a meaningful glucose or insulin effect. That pattern is worth knowing before assuming a small dose delivers a small version of every benefit.

Does a GLP-1 raise the risk of hypoglycemia with type 1 diabetes?

In the liraglutide trials, yes. Symptomatic hypoglycemia increased at every dose of ADJUNCT ONE, and the increase grew with dose. The chart below sets the hypoglycemia rate ratio next to the insulin dose ratio, so the trade-off is visible: the doses that cut insulin most also brought the most lows.

The rate ratios were 1.17 at 0.6 mg, 1.27 at 1.2 mg and 1.31 at 1.8 mg. The ADJUNCT TWO trial by Ahrén and colleagues, also in Diabetes Care in 2016, kept insulin capped rather than titrated and still saw 21.3 versus 16.6 symptomatic hypoglycemia events per patient-year on liraglutide 1.2 mg versus placebo.

The newer semaglutide trials look calmer on this front, possibly because they used automated insulin delivery. In a crossover trial in Nature Medicine in 2025, Pasqua and colleagues found semaglutide did not increase time below 3.9 mmol/L. ADJUST-T1D recorded two severe hypoglycemia events in each arm. A pump that trims insulin as needs fall may be doing work that a fixed injection schedule cannot. If lows after meals are already a pattern, our piece on post-meal blood sugar crashes explains why timing matters.

What is the ketosis and DKA risk?

Ketosis is the safety signal that most limits GLP-1 use in type 1 diabetes. When appetite drops and insulin is cut, the body can start burning fat fast enough to build ketones, sometimes while glucose looks normal. The ADJUNCT ONE authors concluded that higher rates of hypoglycemia and hyperglycemia with ketosis were "thereby limiting clinical use in this group."

The numbers are small but consistent. In ADJUNCT ONE, hyperglycemia with ketosis rose significantly only at 1.8 mg, with a rate ratio of 2.22. In ADJUNCT TWO, it ran at 0.5 versus 0.1 events per patient-year on 1.8 mg versus placebo, using a threshold above 1.5 mmol/L. The semaglutide crossover trial by Pasqua and colleagues had no DKA, but it did record two episodes of recurrent euglycemic ketosis without acidosis during semaglutide use.

The worst outcome in the recent literature involved a drug combination. A 2026 case report by Malik and colleagues in Clinical Case Reports describes a 41-year-old woman with type 1 diabetes who developed severe euglycemic DKA after starting tirzepatide while on empagliflozin and insulin. Her blood pH was 6.96 with glucose of only 190 to 200 mg/dL, and she needed intubation. Vomiting, a common GLP-1 side effect, was the first sign. That overlap is why our sick-day rules article matters even more for anyone using insulin.

How much weight do people with type 1 diabetes lose on a GLP-1?

People with type 1 diabetes lose a moderate amount of weight on GLP-1 medicines, generally less than people without diabetes. ADJUNCT TWO, which held insulin at a capped dose for 26 weeks in 835 people, gives a clean dose ladder for liraglutide.

Weight changed by -2.5, -4.0 and -5.1 kg on 0.6, 1.2 and 1.8 mg, against -0.2 kg on placebo. The newer drugs go further. A real-world study from the Dasman Diabetes Institute by Al Ozairi and colleagues, in Diabetes, Obesity and Metabolism in 2026, followed 250 people with type 1 diabetes and a BMI of 27 or more for 12 months.

Weight fell 10.9% on tirzepatide (35 people), 9.9% on semaglutide (36) and 7.1% on liraglutide (97). HbA1c fell by 0.65%, 0.33% and 0.23%. The 82 people on usual care saw no change, and nobody had severe hypoglycemia or DKA. The authors wrote that "Weight loss appeared less compared with patients without diabetes," and the groups were small and not randomized, so these figures describe one clinic's experience rather than a fair head-to-head comparison.

Do semaglutide and tirzepatide improve time in range?

Semaglutide and tirzepatide both improved time in range in recent type 1 diabetes studies, by single-digit percentage points. The strongest evidence is ADJUST-T1D, a 26-week double-blind trial in 72 adults with a BMI of 30 or higher who all used automated insulin delivery. Participants were randomized to weekly semaglutide up to 1 mg or placebo.

The trial's primary goal combined three targets: time in range above 70%, time below range under 4%, and at least 5% weight loss. Thirty-six percent of the semaglutide group hit all three, against 0% on placebo. Compared with placebo, weight differed by -8.8 kg, time in range by 8.8 points and HbA1c by -0.3 points.

Tirzepatide data are observational so far. Akturk and colleagues at the Barbara Davis Center, writing in Diabetes Technology and Therapeutics in 2026, compared 61 adults with type 1 diabetes on tirzepatide with 54 matched controls. The tirzepatide group reached composite CGM targets at 12 months in 50.8% of cases versus 25.9% of controls.

The gap was 4.6 points at 3 months, 9.0 at 6 months, 6.9 at 9 months and 7.4 at 12 months, without more time below range and with no severe hypoglycemia or DKA. The authors were careful to say that "Proper long-term randomized control trials are needed" before drawing firm conclusions.

What happens after stopping semaglutide with type 1 diabetes?

Stopping semaglutide appears to give back some of the glucose benefit within weeks. Montaser and colleagues followed ADJUST-T1D participants for a 12-week extension and published the results in Diabetes, Obesity and Metabolism in 2026.

Among 16 people who stopped semaglutide, time in range changed by a median of -3.6%, compared with 1.5% in 22 former placebo participants. Glucose variability rose too. Hypoglycemia measures did not differ. The authors concluded that "glycaemic benefits achieved during treatment may not be fully sustained following withdrawal." For anyone thinking of a GLP-1 as a short course, that is a useful data point, and it echoes what weight trials show in people without diabetes.

What does the pooled evidence say?

Pooled across many studies, GLP-1 medicines give modest benefits in type 1 diabetes with rare serious harms. Abdel-Rahman and colleagues gathered 90 studies in a meta-analysis in Diabetes, Obesity and Metabolism in 2026.

GLP-1 medicines lowered HbA1c by 0.56% and body weight by 3.6 kg, increased time in range and reduced insulin needs. Severe hypoglycemia and DKA were rare, and stomach and gut symptoms were the most common side effects. If nausea is the sticking point, our guide to managing nausea on a GLP-1 covers the practical side.

The same analysis flagged SGLT2 inhibitors, another add-on class, for a higher DKA risk in type 1 diabetes, with a risk ratio of 2.19. Put that next to the case report above and the message is clear: stacking a GLP-1 on an SGLT2 inhibitor in type 1 diabetes stacks the ketone risk too.

So what does the evidence support?

The evidence supports a narrow, supervised role. GLP-1 medicines added to insulin produce modest weight loss, small HbA1c drops and better time in range, especially alongside automated insulin delivery. The lowest dose ever tested in a large type 1 trial moved weight but not glucose control or insulin needs.

The risks are specific: more lows when insulin is not adjusted, and ketosis when food intake falls faster than insulin is managed. No trial has tested sub-label microdose protocols in type 1 diabetes, and no regulator has approved these drugs for it. Those facts belong in any conversation with an endocrinologist.

Frequently asked questions

Clinical references

1. Mathieu C, Zinman B, Hemmingsson JU, et al. Efficacy and Safety of Liraglutide Added to Insulin Treatment in Type 1 Diabetes: The ADJUNCT ONE Treat-To-Target Randomized Trial. Diabetes Care. 2016. doi:10.2337/dc16-0691
2. Ahrén B, Hirsch IB, Pieber TR, et al. Efficacy and Safety of Liraglutide Added to Capped Insulin Treatment in Subjects With Type 1 Diabetes: The ADJUNCT TWO Randomized Trial. Diabetes Care. 2016. doi:10.2337/dc16-0690
3. Shah VN, Akturk HK, Kruger D, et al. Semaglutide in Adults with Type 1 Diabetes and Obesity. NEJM Evidence. 2025. doi:10.1056/EVIDoa2500173
4. Pasqua MR, Tsoukas MA, Kobayati A, et al. Subcutaneous weekly semaglutide with automated insulin delivery in type 1 diabetes: a double-blind, randomized, crossover trial. Nature Medicine. 2025. doi:10.1038/s41591-024-03463-z
5. Al Ozairi E, Irshad M, Alkandari J, et al. Weight loss in people with type 1 diabetes over 12 months: Real-world data comparing tirzepatide, semaglutide and liraglutide. Diabetes, Obesity and Metabolism. 2026. doi:10.1111/dom.70172
6. Akturk HK, Karakus KE, Cengiz D, et al. Glucose Control and Continuous Glucose Monitoring Metrics During 12 Months of Treatment with Tirzepatide in Overweight or Obese Patients with Type 1 Diabetes. Diabetes Technology and Therapeutics. 2026. doi:10.1177/15209156251398060
7. Montaser E, Bhasin K, Kruger D, et al. Glycaemic Changes After Semaglutide Discontinuation in Adults With Type 1 Diabetes Using Automated Insulin Delivery: Analysis of the ADJUST-T1D Extension Study. Diabetes, Obesity and Metabolism. 2026. doi:10.1111/dom.71287
8. Abdel-Rahman SM, Al-Shiab R, Shah E, et al. Efficacy and safety of GLP-1 receptor agonists and SGLT2 inhibitors as adjuncts to insulin in type 1 diabetes: Systematic review and meta-analysis. Diabetes, Obesity and Metabolism. 2026. doi:10.1111/dom.70506
9. Malik M, Amjad H, Malik K, et al. Severe Euglycemic Diabetic Ketoacidosis Requiring Intubation After Tirzepatide and SGLT2 Inhibitor Coadministration in a Patient With Type 1 Diabetes Mellitus: A Case Report and Brief Review of the Literature. Clinical Case Reports. 2026. doi:10.1002/ccr3.71929