New type 1 diabetes guidance targets misdiagnosis in adults
New guidance on the management of type 1 diabetes in adults has put greater emphasis on accurate diagnosis amid concerns that the condition is frequently mistaken for type 2 diabetes in people diagnosed later in life.
The updated 2026 consensus report from the American Diabetes Association (ADA) and European Association for the Study of Diabetes (EASD) provides clinicians with clearer recommendations for distinguishing type 1 diabetes from type 2 diabetes and other forms of the condition.
It warns that around 40% of adults diagnosed with type 1 diabetes after the age of 30 are initially misdiagnosed as having type 2 diabetes, with the error more likely to occur among people with overweight or obesity.
Professor Anne Peters, writing panel co-chair and professor of clinical medicine in the Department of Endocrinology/Internal Medicine at the University of Southern California, told Medscape Medical News: “The biggest change is on how to diagnose new-onset type 1 diabetes in adults. It isn’t always straightforward, so we attempted to provide clearer guidance.”
The report advises clinicians to consider adult-onset type 1 diabetes in people with newly diagnosed diabetes who are younger than 35, have a BMI below 25 kg/m² or unintentional weight loss, present with ketoacidosis or glucose levels above 360 mg/dL, or progress rapidly to insulin treatment within three years.
Type 1 diabetes should also be considered whenever there is uncertainty about which type of diabetes a person has.
However, the authors stress that clinicians should not rely on any one characteristic to make a diagnosis, stating: “No single clinical feature confirms type 1 diabetes in isolation.”
Dr Nicholas Argento, director of diabetes technology at Maryland Endocrine and Diabetes, highlighted the importance of not ruling out type 1 diabetes because of a person’s age or weight.
Speaking to Medscape Medical News he said: “It is critical for providers to realise that 30%-40% of those with T1D present after age 30… presentation is often not classic, and many presenting with T1D as adults have obesity, so we should not restrict consideration only to those who have lower BMI.”
The consensus report includes an algorithm recommending islet autoantibody testing for adults suspected of having type 1 diabetes.
The presence of two or more islet autoantibodies, or one strongly positive autoantibody, supports a diagnosis of type 1 diabetes.
Where autoantibodies are negative or only a single low-titre autoantibody is found, clinicians are advised to consider C-peptide testing to assess endogenous insulin production.
According to the algorithm, a C-peptide concentration below 0.6 ng/mL supports a diagnosis of type 1 diabetes. When concentrations are above this threshold, the report provides further guidance to help distinguish between monogenic diabetes, type 2 diabetes and other forms of diabetes.
Professor Peters added: “We talk more about C-peptide testing in the new guidelines than we did before. I look at it clinically — is this person making insulin or not?
“All people with type 1 diabetes and insulin-deficient people with type 2 diabetes could benefit from automated insulin delivery systems and also from SGLT2 inhibitors or GLP-1-based therapies.”
Dr Argento welcomed the diagnostic flow chart but cautioned that C-peptide results need to be interpreted in the appropriate clinical context.
He said C-peptide testing early in the course of diabetes can be misleading because levels may still be normal or low-normal, while severe renal disease can also lead to elevated concentrations.
Experts advise against ‘LADA’ terminology
Another notable change is a recommendation to avoid the term “latent autoimmune diabetes in adults”, or LADA, which has commonly been used to describe slower-onset autoimmune diabetes diagnosed during adulthood.
The report describes LADA as a controversial concept for which there are no universally accepted diagnostic criteria, with considerable variation in clinical presentation and disease progression.
Professor Peters said: “It is not a specific subtype. It is type 1 by definition because it’s autoimmune.”
Dr Argento agreed, saying the use of the term “contributes to confusion rather than clarity”.
Obesity and cardiovascular risk added to guidance
The 2026 update also introduces dedicated sections covering microvascular complication screening, cardiovascular risk management and obesity management.
Although recommendations in these areas are not new, they were not included in the previous 2021 consensus report because management did not differ substantially from wider diabetes guidance.
The new document brings those areas into the adult type 1 diabetes guidance following requests for a more comprehensive resource.
Dr Argento welcomed the inclusion of cardiovascular risk management, describing cardiovascular disease as the leading cause of death among people with type 1 diabetes and an issue that is “often not appreciated”.
He also welcomed the addition of guidance on managing obesity in people with type 1 diabetes.
Other areas have been updated to reflect newer evidence, including psychosocial care, diabetes self-management education, exercise and nutrition.
Detailed recommendations on insulin dosing have not been revised because the guidance provided in the 2021 consensus report remains unchanged.
The updated ADA/EASD consensus report, The Management of Type 1 Diabetes in Adults, has been published in Diabetes Care and Diabetologia.