Why Some Adults With Type 1 Diabetes Are Diagnosed as Type 2—and What's Changing

Type 1 and type 2 diabetes are very different diseases requiring different treatment approaches. Yet in real-world practice, many adults with type 1 diabetes are initially diagnosed with type 2—sometimes for years before the error is caught.

A new study published in Diabetes, Obesity, and Metabolic Care examined how often this happens and why. Researchers at an academic medical center looked at data from 1,077 people who received islet autoantibody testing—a blood test that detects the immune markers characteristic of type 1 diabetes—between July 2024 and June 2025.

The results paint a clear picture: diabetes misclassification in adults is common, and the problem starts with how often—or how seldom—doctors test for type 1 markers in the first place.

The study found striking differences in how children and adults with diabetes are evaluated. Among children undergoing autoantibody testing, 51% were seen in endocrinology clinics and 65% had all four islet autoantibodies measured. In contrast, only 36% of adults were evaluated in endocrinology, and just 6% received testing for all four autoantibodies.

This disparity reflects a real challenge in clinical practice: type 2 diabetes is far more common than type 1 in adults, so doctors may not think to test for type 1 markers. Without that testing, type 1 cases slip through undiagnosed, and patients receive treatment designed for a different disease.

When autoantibody testing was finally done, 309 people tested positive for islet autoantibodies—the hallmark of type 1 diabetes. Of those, 91 individuals (13%) were reclassified from type 2 to type 1 diabetes.

Perhaps most striking: 89% of the people reclassified to type 1 were adults over 18, and 51% of them had gone more than 5 years before receiving the correct diagnosis. This means many adults spent years on type 2 diabetes medications and management strategies that didn't match their actual disease.

This research highlights an important gap in adult diabetes care. Adults with type 1 diabetes—sometimes called latent autoimmune diabetes in adults, or LADA—deserve the same diagnostic thoroughness as children. Autoantibody testing is a straightforward blood test that can clarify diagnosis and guide treatment.

For patients who suspect their diagnosis may be incorrect, or who aren't responding well to type 2 diabetes medications, asking a doctor about autoantibody testing may be worth considering. For healthcare providers, the study suggests that wider use of autoantibody screening in adults could catch more type 1 cases earlier and ensure patients receive appropriate care from the outset.

Source: Diabetes, obesity, and cardiometabolic CARE. Evidence type: PubMed indexed literature. Type1Cure is an information and intelligence hub, not a medical advice service. This article summarizes published research and does not provide diagnosis, treatment, or personal medical guidance. Always talk to your own care team before changing anything about your Type 1 diabetes management.