Treating type 1 diabetes with insulin…and medication?

Insulin is the cornerstone of type 1 diabetes (T1D) treatment. But, did you know that some people with T1D also use other types of medication—called insulin adjuvants—to improve their blood sugar levels or other health issues?

Our research team examined data from the BETTER registry to find out more about these types of treatments and better understand what people with T1D use them, and why.

What is a pharmaceutical adjuvant?

In the context of T1D, a pharmaceutical adjuvant is a treatment which is added to insulin to improve blood sugar levels. It is not meant to replace insulin; rather, it helps to:

• Reduce blood sugar levels (by other means than insulin);
• Reduce the amount of insulin required;
• Lose weight.

An adjuvant can also help manage cardiovascular disease risk factors such as blood pressure and cholesterol.

The treatment for type 2 diabetes (T2D) generally involves a pharmaceutical adjuvant, but these can also be prescribed for the treatment of T1D in certain situations, depending on the doctor’s assessment.

They are part of one of three main groups of drugs.

• Biguanides (e.g., metformin tablets)

This medication is a staple of the treatment for T2D. It cannot replace insulin, but it helps the body to better respond to the action of insulin. This can be particularly helpful for people who have insulin resistance, i.e., when insulin doesn’t seem to work as well. With a better response to insulin, it is sometimes possible to reduce the doses and stabilize blood sugar levels.

Studies have shown that metformin can slightly reduce blood sugar levels and insulin intake in people with T1D, but the overall benefits remain negligible.

To help with the digestive side effects (e.g., diarrhea), it is recommended to adjust the dose gradually and to take it at mealtime.

People with renal insufficiency must avoid or stop taking this drug, as it is not indicated for this condition.

• Glucagon-Like Peptide-1 (GLP-1) agonists (e.g., injectable liraglutide or semaglutide)
  

  These drugs mimic the GLP-1 hormone, which the body secretes naturally. This hormone helps the secretion of insulin while we eat, slows down digestion and reduces appetite. This combined action often reduces the post-prandial blood sugar spike and can help shed a few pounds for easier diabetes management. Studies have shown that just like metformin, GLP-1 agonists provide modest benefits to people with T1D in terms of reducing blood sugar levels and insulin intake. However, in terms of weight loss, the results are significant, and similar to those achieved by people with T2D. Digestive side effects such as nausea can often be mitigated by adjusting the dose gradually, depending on symptoms. While this group of drugs reduces the risk of cardiovascular disease and renal insufficiency in people with T2D, it is not known if people with T1D can see similar benefits.

• SGLT2 inhibitors (e.g., empagliflozin or dapagliflozin tablets)

These drugs help the body eliminate excess glucose in urine, which can reduce blood sugar levels and help lose some weight. However, they also increase the risk of ketoacidosis even if blood sugar levels are not high. Although it is rare, it is serious and requires strict monitoring, especially with people with T1D. For this reason, Health Canada does not recommend their use for T1D.

The most common side effect is genital infections, i.e., vaginitis (women) and balanitis (men). They remain infrequent, but the risk is doubled.

SGLT2 inhibitors have proven beneficial for cardiovascular and renal health in people with T2D. However, it is not known if people with T1D see similar benefits.

These types of treatments are not one-size-fits-all and come with risks that can be significant. They must be prescribed and monitored by a healthcare team specialized in T1D.

What does the study say?

The study looked at the data pertaining to 1,463 adults living with T1D and signed up to the Canadian BETTER registry. About 1 person out of 7 used one pharmaceutical adjuvant on top of insulin. Among those:

• 41% used metformin;
• 26% used a GLP-1 agonist;
• 18% used an SGLT2 inhibitor;
• 15% used at least two of these medications.

There were some common traits among these people. On average, they were a bit older (47 years old vs. 43 years old) and their body mass index (BMI) was a bit higher (29.1 vs. 25.1 kg/m2) than those who don’t use these medications, which can indicate insulin resistance. They also had higher risk factors for cardiovascular health, e.g., higher blood pressure, higher cholesterol or a history of cardiovascular or blood vessel diseases.

In terms of HbA1c levels (blood sugar average from past three months) or time since diagnosis, both groups were more or less similar. The study was not able to determine whether the pharmaceutical adjuvants helped lower HbA1c levels or whether they had limited impact on blood sugar levels.

It should also be noted that among people who used SGLT2 inhibitors, the incidence of reported ketoacidosis episodes was not higher than that of other groups, according to self-reported data from the registry.

An option for some…

It is rather frequent for adults with T1D to use insulin as well as other medications, especially in the presence of other health issues such as overweight, insulin resistance and cardiovascular risk.

Although they’re not a one-size-fits-all solution, these treatments, in some cases, can help reduce insulin intake or stabilize blood sugar levels, or help with other health issues. Their use must be closely monitored, as some carry risks, for instance, the risk of ketoacidosis with SGLT2 inhibitors. Ongoing studies are trying to determine whether this risk can be reduced and whether this group of drugs can slow down renal damage. We should have access to more information in the next few years.  

Discuss these options with a healthcare team specialized in T1D; they can help you better assess the pros and cons while considering your needs, your health status and your personal preferences.

You live with T1D and would like to help advance research? If you haven’t done so yet, consider signing up for the BETTER registry now. Each and every voice matters!

References

• Summary presented at ADA 2025 : Factors Associated with the Use of Adjunct-to-Insulin Glucose-Lowering Agents in Patients with Type 1 Diabetes Mellitus, Jessica Liu et al.