Reading Between the Lines: Closing the T1D Misdiagnosis Gap

Our modern classifications of type 1 diabetes (T1D) first began to take shape in the late 1970s. Following years of research into the disease's underlying causes, the scientific community finally reached consensus, standardizing the nomenclature and definitions for diabetes mellitus: type 1 as the autoimmune condition and type 2 as the metabolic disorder of insulin resistance and deficiency.

It was a landmark achievement in endocrinology, which has since helped us identify nearly 2 million individuals currently living with T1D in the United States. Yet despite another half-century of progress since this delineation solidified, a troubling reality persists: public awareness gaps between type 1 and type 2 diabetes remain as wide as ever in 2026.

To bridge the gap, healthcare providers must continue expanding our understanding of this disease and its nuances.As science continues to evolve, so must we, starting with our approach to diagnosis.

Recent studies from Sanofi presented at the American Diabetes Association (ADA) 2026 Scientific Sessions provide compelling new evidence for why we need to expand how we think about diabetes diagnosis. Below are two key areas where evidence is challenging our diagnostic assumptions and sharpening the definitions that guide clinical practice.

Challenging Assumption Leading to Misdiagnosis

Many in the diabetes community recognize that when it comes to diagnosis, assumptions have impact. Age, weight, and lifestyle factors have all influenced how healthcare providers initially diagnose their patients, despite mounting evidence that T1D demographics may be less restrictive than we once believed.

As a result, far too many individuals are misdiagnosed with prediabetes or T2D when they actually have T1D.Unfortunately, I've witnessed this firsthand, when someone close to me was misdiagnosed with T2D in her 40s, only to be correctly identified with T1D years later.

It was a jarring experience that stemmed from a startlingly common misconception: that adults don't get T1D; however, she is far from alone: Presented at ADA, recent findings from a global RECLASS study reveal that approximately 1 in 46 individuals initially diagnosed with prediabetes or T2D were later reclassified as T1D.

These numbers may seem small on paper, but they represent a meaningful human impact. Misclassification of T1D can potentially result in serious health consequences, including diabetic ketoacidosis (DKA), hospitalization, and long-term complications. This is precisely why healthcare providers must look beyond surface-level indicators such as age, weight, or lifestyle—and recognize the nuanced presentations that distinguish T1D from T2D.

Considering GDM As Potential Early Predictor

Another emerging area of focus in T1D diagnosis is gestational diabetes (GDM), which is a condition in which diabetes is first identified during pregnancy. In fact, recent findings from the T1D Incidence after Gestational Diabetes Diagnosis: A Real-World Longitudinal U.S. Study reveal that up to 0.78% of women were diagnosed with T1D within 10 years of a GDM diagnosis.

In the study alone, this translated to 575 women, each of whom could have benefitted from earlier disease knowledge and the opportunity to prepare for the future. What does this data tell us?

Put simply, we should take a longer view beyond an initial GDM diagnosis and consider the role that T1D autoantibody screening could play in early risk detection for these individuals. The opportunity here is meaningful.

Incorporating T1D autoantibody screening into early postnatal care could offer a practical pathway for early risk detection that is worth exploring as part of routine postpartum follow-up.

Moving from Classification to Clarity

Fifty years ago, we standardized the definitions that shaped modern diabetes care. Today, the science is asking us to go further. As our understanding of T1D, T2D, and GDM continues to evolve, we must be willing to look beyond rigid classifications and embrace the gray areas that exist between them.

Even well-intentioned clinical judgment can miss what's happening beneath the surface if we rely on assumptions rather than evidence. By adopting a more individualized approach, healthcare providers have an opportunity to reduce misdiagnosis and give patients the knowledge they need to prepare for the road ahead.

About the Author

Jessica Dunne, US Medical, Autoimmune Diabetes Medical Director at Sanofi.