Type 1 Diabetes: A Brief Overview

Type 1 diabetes (T1D) is an autoimmune disease where the immune system mistakenly destroys the beta cells in the pancreas that produce insulin. This destruction leads to an absolute deficiency of insulin, which is essential for moving glucose from the bloodstream into cells for energy. Without insulin, blood glucose levels rise dangerously high, a condition known as hyperglycemia. People with T1D depend on lifelong insulin therapy—delivered via injections or an insulin pump—to manage their blood sugar and stay alive. Despite advances in insulin formulations and delivery systems, achieving stable glucose control remains challenging. Many individuals experience frequent hypoglycemic episodes (low blood sugar) or struggle with weight gain and wide glucose fluctuations. This reality drives the search for adjunctive therapies that can complement insulin.

What Are SGLT2 Inhibitors?

Sodium-glucose cotransporter 2 (SGLT2) inhibitors, often called gliflozins, are a class of medications originally approved for the treatment of type 2 diabetes. They work by a unique, insulin-independent mechanism: they block the SGLT2 protein in the proximal tubule of the kidneys. Under normal conditions, SGLT2 is responsible for reabsorbing about 90% of the filtered glucose back into the bloodstream. When SGLT2 is inhibited, a substantial amount of glucose remains in the urine and is excreted. This lowers blood glucose levels regardless of insulin secretion or action. Additionally, SGLT2 inhibitors promote caloric loss through glucosuria, which can lead to modest weight reduction and improved blood pressure control. Drugs in this class include canagliflozin, dapagliflozin, empagliflozin, and ertugliflozin. Their well-established safety and efficacy in type 2 diabetes have sparked interest in their potential application to type 1 diabetes.

Potential Benefits for Type 1 Diabetes

Applying SGLT2 inhibitors to T1D could offer several advantages beyond glucose lowering. Because these drugs work independently of insulin, they might help reduce blood sugar without requiring additional insulin—thus lowering total daily insulin doses. This is particularly appealing because the weight gain often associated with intensified insulin therapy could be mitigated through the caloric loss from glucosuria. Moreover, by reducing the wide postprandial glucose swings, SGLT2 inhibitors may improve time in range (the percentage of time blood glucose stays within a target range). Some studies have also suggested improvements in HbA1c, a marker of long-term glucose control. Another theoretical benefit involves the reduction of insulin-induced hypoglycemia. Since SGLT2 inhibitors do not stimulate insulin secretion, they are not intrinsically hypoglycemic; however, when used alongside insulin, the risk of hypoglycemia exists if insulin doses are not adjusted appropriately. Nonetheless, careful dose reduction of mealtime insulin may lower the frequency of hypoglycemic events. These potential benefits make SGLT2 inhibitors an attractive adjunctive therapy for selected patients with T1D.

Weight Management and Cardiovascular Effects

Weight management is a significant concern for many individuals with T1D, as intensive insulin therapy often promotes weight gain. The glucosuria induced by SGLT2 inhibitors leads to a daily caloric loss of roughly 200–300 calories, translating into modest but clinically meaningful weight reduction over several months. This effect has been consistently observed in type 2 diabetes trials and is also seen in T1D studies. Additionally, SGLT2 inhibitors have demonstrated cardiovascular benefits in type 2 diabetes, including reductions in heart failure hospitalizations and major adverse cardiac events. Although the cardiovascular profile in T1D is less clear, there is reason to suspect similar benefits given the high cardiovascular risk in people with T1D, especially those with poor glycemic control or nephropathy. However, dedicated cardiovascular outcome trials in T1D are lacking, so this remains an area of ongoing research.

Challenges and Risks: The DKA Problem

The primary safety concern with using SGLT2 inhibitors in type 1 diabetes is an increased risk of diabetic ketoacidosis (DKA). DKA is a life-threatening condition characterized by hyperglycemia, metabolic acidosis, and high levels of ketones (acids produced when the body breaks down fat for energy). In T1D, DKA typically occurs during severe insulin deficiency, but SGLT2 inhibitors can precipitate what is known as “euglycemic DKA”—a state where blood glucose levels are not markedly elevated (often below 250 mg/dL) yet ketones are dangerously high. This is particularly dangerous because the typical warning signs (high blood sugar) are absent, delaying diagnosis and treatment. The mechanism involves reduced renal clearance of ketones and increased ketone production due to the altered metabolic state. Clinical trials have reported DKA rates of 4–6% in patients with T1D using SGLT2 inhibitors, compared to less than 1% in placebo groups. To mitigate this risk, strict patient selection is essential: candidates must have well-controlled T1D, be adherent to insulin therapy, understand sick-day rules, and have a system for monitoring ketones (e.g., blood ketone meters). Even with precautions, the U.S. Food and Drug Administration (FDA) has not approved any SGLT2 inhibitor solely for T1D, though some (e.g., dapagliflozin) have received approval in Europe with stringent risk management measures [FDA safety communication].

Other Adverse Effects

Beyond DKA, SGLT2 inhibitors can cause genital mycotic infections (e.g., yeast infections) due to the high glucose concentration in urine. Urinary tract infections are also more common, though the absolute risk is modest. Dehydration and hypotension can occur, especially in the elderly or those on diuretics, because of the osmotic diuresis. Rare but serious events include Fournier's gangrene (a necrotizing infection of the perineum) and acute kidney injury, prompting the FDA to issue boxed warnings. These risks underscore that SGLT2 inhibitors are not a simple “add-on” drug for T1D; they require careful patient education, monitoring, and the ability to detect and manage ketones promptly.

Clinical Trials and Evidence

Several clinical trials have investigated SGLT2 inhibitors in T1D, and while results are promising in terms of glycemic improvement, the DKA signal remains a barrier. The inTandem program (using sotagliflozin, a dual SGLT1/2 inhibitor) and the DEPICT program (using dapagliflozin) are among the largest. In the DEPICT-1 and DEPICT-2 trials, dapagliflozin 5 mg and 10 mg as adjunctive therapy to insulin achieved reductions in HbA1c of approximately 0.4–0.5% over 24 weeks, along with reductions in total daily insulin dose and body weight [Dandona et al., Diabetes Care, 2018]. However, DKA occurred more frequently in the dapagliflozin groups (up to 4%) compared to placebo (0.1%). Similar findings were reported for sotagliflozin, although it was ultimately not approved in the U.S. for T1D due to concerns about DKA. Empagliflozin has also been studied in the EASE program (Empagliflozin as Adjunctive to insulin therapy in type 1 diabetes), showing reductions in HbA1c and weight but again with an elevated DKA risk [Rosenstock et al., Diabetes Care, 2019]. Currently, only dapagliflozin is approved for T1D in Japan and parts of Europe under specific conditions — for example, in patients with a body mass index ≥27 kg/m² who are on intensive insulin therapy and have adequate kidney function. In the United States, the FDA has not approved any SGLT2 inhibitor for T1D, but physicians may prescribe them off-label with careful monitoring, though this is controversial.

Key Inclusion Criteria in Trials

Reviewing trial protocols reveals that participants were generally well-selected: they had well-controlled T1D (HbA1c 7.0–9.0%), were using either multiple daily injections or pump therapy, had a documented ability to monitor ketones, and were trained to adjust insulin doses. Those with a history of DKA in the previous six months or with hypoglycemia unawareness were excluded. This selection is critical, because in real-world practice, not every patient with T1D is a suitable candidate. Adoption of mandatory ketone monitoring and a reduced insulin dose upon initiating the drug were part of the safety protocols. These measures reduced but did not eliminate DKA.

Regulatory Status and Guidelines

As of 2025, no SGLT2 inhibitor has received FDA approval for type 1 diabetes. The European Medicines Agency (EMA) has granted marketing authorization for dapagliflozin (as Forxiga) in T1D, but only for patients with a BMI ≥27 kg/m² who are inadequately controlled on insulin, and it must be used in conjunction with a structured ketoacidosis risk management program. The Australian Therapeutic Goods Administration (TGA) has also approved dapagliflozin 5 mg as an adjunct to insulin for similar patients. In contrast, the American Diabetes Association (ADA) Standards of Care currently recommend against routine use of SGLT2 inhibitors in T1D due to the DKA risk, though they acknowledge that in selected individuals with high cardiovascular risk or excess weight, it may be considered off-label with intensive education and ketone monitoring [ADA Pharmacologic Approaches, 2024].

Future Directions and Ongoing Research

The potential of SGLT2 inhibitors in T1D continues to be explored. Researchers are investigating lower doses of existing drugs to minimize DKA risk while maintaining glycemic benefit. For instance, low-dose empagliflozin (2.5 mg) has shown a better safety profile in the EASE trials, with a lower incidence of DKA compared to the currently approved 10 mg and 25 mg doses. Another avenue is the development of selective SGLT1 inhibitors or dual SGLT1/2 inhibitors that may further reduce postprandial glucose excursions and have a more favorable risk-benefit balance. Additionally, combining SGLT2 inhibitors with automated insulin delivery (hybrid closed-loop systems) is being studied, as the algorithm could automatically adjust insulin delivery to counteract the increased ketone production. Early results suggest that such a combination could improve time in range while reducing the DKA risk, as the closed-loop system provides tighter control. Large-scale real-world registries are also collecting data on off-label use to better understand the incidence of DKA in less controlled settings. Finally, the use of SGLT2 inhibitors to preserve beta-cell function in newly diagnosed T1D is a new frontier; small studies suggest that the reduction in glucose toxicity may help residual insulin secretion last longer, delaying disease progression.

Patient Selection: Who Might Benefit?

Given the risks, patient selection is paramount. Ideal candidates for SGLT2 inhibitor therapy in T1D are adults with well-controlled diabetes (HbA1c <8.5%), no history of recent DKA or recurrent DKA, normal or near-normal kidney function (eGFR >60 mL/min/1.73 m²), a BMI ≥25 kg/m², and the willingness and ability to monitor blood ketones (e.g., using a precision meter) and follow sick-day rules (stopping the drug during illness or if unable to eat). They should also have a robust understanding of insulin dose adjustment, especially reducing prandial insulin upon initiation. Patients with very labile glucose control, hypoglycemia unawareness, or a history of eating disorders are generally not suitable. The decision must be individualized, weighing the potential improvements in HbA1c, weight, and insulin dose reduction against the real risk of DKA. In some European countries where dapagliflozin is approved, prescribing is restricted to diabetologists or endocrinologists with experience in T1D and ketoacidosis management.

Practical Considerations for Clinicians

For clinicians contemplating off-label use of SGLT2 inhibitors in T1D, several precautions are non-negotiable. First, obtain informed consent explaining the risk of euglycemic DKA and the need for ketone monitoring. Second, start at the lowest available dose (e.g., dapagliflozin 5 mg or empagliflozin 2.5 mg) and reduce the mealtime insulin dose by 10–20% to avoid hypoglycemia. Third, teach the patient to test for ketones (preferably blood beta-hydroxybutyrate) on a daily basis during the first week, then whenever blood glucose is persistently above 250 mg/dL or if they feel unwell. Fourth, advise patients to stop the medication at least 24 hours before surgery, during episodes of vomiting or illness, and if they cannot eat or drink normally. Finally, arrange close follow-up within 2–4 weeks to review glucose logs, ketone readings, and side effects. These measures can reduce but not eliminate the DKA risk.

Conclusion

While SGLT2 inhibitors are not yet approved for routine use in type 1 diabetes, ongoing research suggests they could become a valuable addition to treatment options for carefully selected patients. The potential advantages—improved glycemic control, weight reduction, lower insulin requirements, and possible cardiorenal protection—are compelling. However, the elevated risk of diabetic ketoacidosis, particularly the atypical euglycemic form, remains a significant barrier to widespread adoption. As clinical trials refine dose strategies and risk mitigation protocols, and as real-world evidence accumulates, the role of SGLT2 inhibitors in T1D may expand. For now, decisions about their use must be made on a case-by-case basis, with meticulous patient education, monitoring, and shared decision-making. With further research and possibly the development of T1D-specific SGLT2 therapies, these drugs may one day offer a safer way to help people with type 1 diabetes achieve better outcomes and quality of life.