Semaglutide for Type 1 Diabetes: Potential Benefits Explored

Semaglutide, the drug behind brand names like Ozempic and Wegovy, was designed for type 2 diabetes and obesity, but a growing body of clinical evidence suggests it can meaningfully help people with type 1 diabetes too. Recent randomized trials and real-world studies show improvements in blood sugar control, reduced insulin requirements, and significant weight loss when semaglutide is added to insulin therapy. The drug is not approved for type 1 diabetes anywhere in the world, making all current use off-label, and the research is still catching up with clinical practice in interesting ways.

What the Trials Show for Blood Sugar Control

The most consistent finding across studies is a reduction in HbA1c, the marker that reflects average blood sugar over roughly three months. A 2025 systematic review and meta-analysis pooling data from adults with type 1 diabetes who were overweight or obese found that HbA1c dropped by about 0.54% after three months, 0.55% after six months, and 0.60% after twelve months of semaglutide use.¹ Those numbers might sound modest compared to the HbA1c drops seen in type 2 diabetes trials, but in type 1 diabetes, where insulin is already doing the heavy lifting, squeezing out an extra half-percentage-point improvement is harder than it sounds.

A double-blind crossover trial published in Nature Medicine tested weekly semaglutide in people with type 1 diabetes who were using automated insulin delivery systems, sometimes called closed-loop pumps. Compared to placebo, semaglutide reduced HbA1c by 0.5 percentage points.² A separate randomized trial in adults with type 1 diabetes and obesity found a somewhat smaller difference between semaglutide and placebo of 0.3 percentage points for HbA1c, but that trial also reported a striking 8.8 percentage-point increase in time-in-range on continuous glucose monitoring.³ Time-in-range, the percentage of the day spent with blood glucose between 70 and 180 mg/dL, is increasingly seen as a more practical measure of daily glucose management than HbA1c alone.

Time in Range and What It Means Day to Day

The Nature Medicine crossover trial found that semaglutide increased time-in-range by 4.8 percentage points compared to placebo when participants were on automated insulin delivery. That improvement came entirely from a reduction in time spent high rather than an increase in time spent low.⁴ In practical terms, 4.8 extra percentage points translates to roughly an additional hour per day in the target glucose zone. The mean glucose level and glucose variability both went down with semaglutide, which is the kind of flattening of the glucose curve that people with type 1 diabetes often pursue through diet, timing, and pump settings.

For context, a two-year real-world study tracking adults with type 1 diabetes on semaglutide found even more dramatic shifts: time-in-range (70–180 mg/dL) improved from 46% to 71%, and the tighter range of 70–140 mg/dL improved from about 28% to 48%. Glucose variability, measured by coefficient of variation, fell from 46% to about 34%.³ Those are large improvements, though real-world studies include selection effects: the patients who stay on a medication for two years tend to be the ones responding well to it.

How Insulin Requirements Change

One of the more striking effects of semaglutide in type 1 diabetes is a reduction in how much insulin people need. A post hoc analysis of the ADJUST-T1D trial, published in Diabetes Care, found a 22.6% reduction in total daily insulin dose over 26 weeks in the semaglutide group. Bolus insulin, the doses taken around meals, dropped by about 31%, while basal insulin fell by roughly 16%.⁵ That bolus-dominant reduction makes sense: semaglutide slows gastric emptying and reduces appetite, both of which dampen post-meal glucose spikes and reduce the amount of mealtime insulin the pump or the person needs to deliver.

The same analysis teased apart how much of the insulin reduction was a direct pharmacological effect versus how much came indirectly from weight loss. Early on, at week four, the vast majority of the reduction (about 83%) was a direct drug effect. By week 26, it was roughly an even split, with weight loss accounting for about half of the insulin savings.⁵ The two-year real-world study mentioned earlier observed total daily insulin dropping from 1.4 to 0.7 units per kilogram per day, which is a halving of the dose.

Less insulin generally means less risk of insulin-driven weight gain and potentially fewer hypoglycemic episodes. For anyone who has struggled with the cycle of taking more insulin, gaining weight, then needing even more insulin, a tool that breaks that pattern is meaningful.

Weight Loss

Weight management in type 1 diabetes is an underappreciated challenge. Insulin is a growth hormone, and intensive insulin therapy tends to promote weight gain over time. A broader meta-analysis of GLP-1 receptor agonists as adjuncts to insulin in type 1 diabetes found an average weight reduction of about 3.6 kilograms.⁶ Individual trials report somewhat higher numbers. The randomized trial of semaglutide in type 1 diabetes with obesity found a weight difference of 8.8 kilograms (about 19 pounds) between semaglutide and placebo at 26 weeks.³ A retrospective study tracking off-label semaglutide use over 12 months reported about 9% body weight loss in semaglutide users.⁷

The weight loss is especially relevant because the prevalence of overweight and obesity in people with type 1 diabetes has been rising for decades, paralleling trends in the general population. Until recently, clinicians sometimes thought of type 1 diabetes as a “lean” disease, but that framing increasingly misses the mark.⁸ Carrying excess weight in type 1 diabetes worsens insulin resistance, increases cardiovascular risk, and complicates dosing. A medication that addresses both glucose and weight fills a gap that insulin alone cannot.

Safety, Hypoglycemia, and the Ketoacidosis Question

The fear with any add-on therapy in type 1 diabetes is that improving blood sugar control might come at the cost of more dangerous lows. The evidence so far is reassuring on that front. In the Nature Medicine crossover trial, there was no increase in time spent below 3.9 mmol/L (about 70 mg/dL) or below 3.0 mmol/L (about 54 mg/dL) with semaglutide compared to placebo.⁹ The broader meta-analysis of GLP-1 receptor agonists in type 1 diabetes similarly found that severe hypoglycemia was rare.⁶ The combination of automated insulin delivery with semaglutide likely helps here: the pump can reduce basal insulin delivery in real time when glucose starts to trend low, blunting the risk that lower insulin needs would lead to stacking.

Diabetic ketoacidosis, or DKA, is the other serious concern. DKA occurs when the body runs short on insulin and starts breaking down fat for fuel, producing dangerous levels of ketones. When you reduce insulin doses in type 1 diabetes, you are walking closer to that edge. The meta-analysis found that DKA was rare with GLP-1 receptor agonists, which contrasts with SGLT2 inhibitors, the other major class of adjunct drugs studied in type 1 diabetes, where DKA risk was roughly doubled.⁶ Still, the clinical community treats this with appropriate caution, and monitoring for ketones during dose escalation is standard advice in consensus guidelines.

Gastrointestinal Side Effects and How They Affect Daily Management

The most common side effects of semaglutide in type 1 diabetes are the same as in type 2: nausea, reduced appetite, and other gut-related complaints. One study comparing patient-reported adverse events with semaglutide and tirzepatide in type 1 diabetes found that gastrointestinal side effects did not differ between the two drugs. Young adults and women were more likely to report GI problems regardless of which medication they were on.¹⁰

But there is an added wrinkle for type 1 diabetes that does not exist in type 2. People with type 1 diabetes who use insulin pumps or pens must estimate their carbohydrate intake before meals and dose insulin accordingly. Nausea and a fear of vomiting can make it difficult to accurately predict how much you are about to eat, which in turn makes it harder to calculate the right bolus. A qualitative study of patient experiences from a randomized trial found that nausea and fear of vomiting were real barriers to accurate pre-meal carbohydrate estimation and bolus dosing.¹¹ This is a practical management issue that gets lost in the headline numbers: even if the overall glucose outcomes improve, the daily experience of dosing insulin can become more uncertain during the weeks when GI side effects are at their worst, which is typically during dose escalation.

Residual Beta-Cell Function and Who Benefits Most

Not everyone with type 1 diabetes has zero insulin production. Many people, especially those diagnosed more recently, retain some residual beta-cell function. This turns out to be an important predictor of how well GLP-1 receptor agonist therapy works. A review of the two largest liraglutide trials in type 1 diabetes (over 2,200 participants combined) found that HbA1c dropped by about 0.6% in people with residual beta-cell function, which was meaningfully greater than the reduction in people without it. Residual beta-cell function was the only variable that consistently predicted the glycemic benefit, regardless of starting HbA1c, BMI, or insulin regimen.¹²

This makes biological sense. GLP-1 receptor agonists stimulate insulin secretion from beta cells, but they can only do that if there are beta cells still producing insulin. In someone whose autoimmune disease has destroyed virtually all beta-cell mass, that particular benefit is unavailable, and any glycemic improvement would come from other mechanisms like slowed gastric emptying, appetite reduction, and glucagon suppression. The practical implication is that semaglutide may be most useful if started earlier in the disease course, while some beta-cell function remains, rather than decades after diagnosis when the pancreas has been fully depleted.

How Semaglutide Compares to SGLT2 Inhibitors

SGLT2 inhibitors such as dapagliflozin and sotagliflozin are the other class of drugs that has received significant attention as add-on therapy for type 1 diabetes. Dapagliflozin was briefly approved for type 1 diabetes in Europe (though it was later withdrawn from that indication in many markets), and sotagliflozin has shown benefits in trials. Comparing these classes head-to-head is useful for understanding where semaglutide fits.

The meta-analysis that evaluated both classes side by side found that GLP-1 receptor agonists produced greater weight loss (about 3.6 kg versus 2.5 kg for SGLT2 inhibitors) and a larger HbA1c reduction (0.56% versus 0.38%). SGLT2 inhibitors, on the other hand, produced a larger improvement in time-in-range (8.6 percentage points). The biggest differentiator was safety: SGLT2 inhibitors roughly doubled the risk of DKA, while GLP-1 receptor agonists did not.⁶ A real-world study comparing the two classes over an average of about 30 months per patient found comparable HbA1c reductions but confirmed the DKA difference: 12.8% of SGLT2 inhibitor users experienced DKA compared to 3.9% of GLP-1 receptor agonist users.¹³ Discontinuation rates due to side effects were similar between the groups, around 27%.

The DKA disparity is the single biggest reason many clinicians now lean toward GLP-1 receptor agonists as the preferred adjunct class. DKA in type 1 diabetes can be life-threatening, and the mechanism by which SGLT2 inhibitors provoke it, by causing glucose to spill into the urine while masking the usual warning signs, makes it particularly insidious. GLP-1 receptor agonists avoid that specific trap.

Adolescents and Younger Patients

Almost all of the trial data on semaglutide in type 1 diabetes comes from adults. For adolescents, the evidence is limited to case reports and small case series. A report published in Pediatrics described two adolescents with type 1 diabetes and obesity who were treated with semaglutide for 12 months. Both showed improvements in glycemic control, weight, and insulin requirements, with no adverse events reported.¹⁴ Two patients is not a trial, and the authors appropriately called for larger studies to figure out optimal dosing, long-term safety, and effects on growth and body composition.

The adolescent population is particularly tricky. Puberty-driven insulin resistance means that teenagers with type 1 diabetes often need surprisingly high insulin doses and gain weight faster than expected. At the same time, the psychological burden of managing a chronic disease during adolescence is heavy, and the appetite-suppressing effects of GLP-1 receptor agonists raise reasonable questions about disordered eating that have not yet been studied in this group. Clinicians prescribing off-label for younger patients are working without a map.

Cardiovascular and Kidney Disease

People with type 1 diabetes face elevated cardiovascular and kidney disease risk even when blood sugar is well controlled. Semaglutide has shown clear cardiovascular and kidney benefits in type 2 diabetes trials, but whether those benefits transfer to type 1 diabetes is unknown. No completed cardiovascular outcome trial exists for semaglutide in type 1 diabetes.

That may change. The Steno 1 study is a multicenter randomized trial now underway that tests an intensified care strategy combining semaglutide, sotagliflozin, and finerenone in high-risk individuals with type 1 diabetes. The study aims to determine whether this combination can reduce major cardiovascular events, heart failure hospitalization, kidney disease progression, and death.¹⁵ Results are years away, but the trial’s design reflects the growing clinical hypothesis that the metabolic benefits seen in the shorter glycemic trials should translate into long-term protection of the heart and kidneys.

The Practical Reality of Off-Label Use

Semaglutide has no regulatory approval for type 1 diabetes in any country. Every prescription in this context is off-label, which creates real-world friction. Insurance coverage is inconsistent and often difficult to obtain. Prior authorization requests may be denied because the medication is not indicated for the patient’s listed diagnosis. Some clinicians have reported listing obesity as the primary indication when the patient qualifies, which navigates the coverage problem but introduces its own complexities in medical records. A consensus report on the safe use of GLP-1 and dual GLP-1/GIP receptor agonists in type 1 diabetes has been developed to help clinicians navigate these issues.¹⁶

Drug manufacturers have shown limited interest in pursuing a type 1 diabetes indication for semaglutide. The type 1 diabetes population is roughly a tenth the size of the type 2 market, and the regulatory pathway would require dedicated phase 3 trials. The clinical community has essentially moved ahead of the regulatory system, with off-label use growing rapidly, driven by both clinician interest and patient demand. The evidence base is catching up through investigator-initiated trials and retrospective analyses, but the gap between practice and formal approval may persist for years.

Tirzepatide as a Comparison and Possible Alternative

Tirzepatide, which acts on both GLP-1 and GIP receptors, has also been studied off-label in type 1 diabetes and may offer even greater weight loss. The retrospective study that tracked both drugs over 12 months found that tirzepatide users lost about 21% of their body weight compared to about 9% for semaglutide users. HbA1c reductions were broadly similar between the two, with tirzepatide showing a slightly larger drop of 0.68% versus 0.54% for semaglutide.⁷ Whether the additional weight loss from tirzepatide translates into better long-term metabolic or cardiovascular outcomes in type 1 diabetes is not yet clear.

The GI side effect profiles of the two drugs appear similar in the type 1 diabetes population. The study comparing patient-reported adverse events found no significant difference in gastrointestinal complaints between semaglutide and tirzepatide, and the proportion of patients who had to reduce their dose because of side effects was also comparable.¹⁰ For clinicians deciding between the two, the choice may ultimately hinge on access, insurance coverage, and the patient’s weight-loss goals more than on any proven difference in glycemic efficacy.