A new 2026 updated consensus report from the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD) addresses diagnosis and management of type 1 diabetes (T1D) in adults, with a major focus on differentiating T1D from other types of diabetes, including type 2 diabetes (T2D), in adults with new-onset diabetes.

“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,” writing panel Co-Chair Anne L. Peters, MD, professor of clinical medicine in the Department of Endocrinology/Internal Medicine, University of Southern California, Los Angeles, told Medscape Medical News.

The report was published both in the ADA’s journal Diabetes Care and in the EASD’s Diabetologia. It updates the first such guidance, which was published online in 2021.

Asked to comment on the new statement, Nicholas B. Argento, MD, director of diabetes technology at Maryland Endocrine and Diabetes in Columbia, told Medscape Medical News, “I applaud this effort to update the adult T1D guidelines. It is thorough, well balanced, and will be a great read for anyone who sees those with T1D.”

New-Onset T1D in Adults Often Misdiagnosed

The document advises considering adult-onset T1D among individuals with new-onset diabetes who are younger than 35 years, who have a BMI < 25 or unintentional weight loss, who have ketoacidosis or glucose > 360 mg/dL on presentation, who have rapid (within 3 years) progression to insulin therapy, or who have any uncertainty about diabetes type.

However, the document also points out that misdiagnosis of T1D as T2D in adults occurs in about 40% of those diagnosed after age 30 and that this error is more likely in those with overweight or obesity. “No single clinical feature confirms type 1 diabetes in isolation,” the authors cautioned.

Argento commented, “It is critical for providers to realize 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. Seventy percent of adults are overweight or obese, so an adult T1D is more likely to be overweight than underweight.”

An algorithm in the report advises that adults suspected to have T1D be tested for islet autoantibodies (IAbs). If there are two or more, or if one is strongly positive, T1D is the diagnosis. If negative for IAbs or if just a single low-titer IAb is present, C-peptide testing should be considered. If < 0.6 ng/mL, T1D is the diagnosis. If the C-peptide level is > 0.6 ng/mL, further guidance is provided for distinguishing monogenic diabetes from T2D or other types.

“We talk more about C-peptide testing in the new guidelines than we did before,” said Peters. “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.”

Argento said the graphic flow sheet was “well put together,” adding, “when measuring islet autoantibodies, one has to be cautious if they are low-grade positive because the person may still have T2D. But [the authors] cover this very nicely in the full text. The IAb tests are highly sensitive if definitely positive.”

Regarding C-peptide testing, Argento pointed out that “it can lead to misinterpretation if checked early in the course [of the disease], where it can still be normal or low normal, but not likely after 3 years. It can be elevated in severe renal disease, so needs to be used with caution in that group.”

Avoid Using the Term ‘LADA’

The guidance discourages the use of the term “latent autoimmune diabetes in adults” (LADA), which often refers to slower-onset T1D in adults. “LADA is a controversial concept with no universally accepted diagnostic criteria and considerable heterogeneity in clinical presentation and progression,” the authors wrote in the paper.

Peters told Medscape Medical News, “It is not a specific subtype. It is type 1 by definition because it’s autoimmune.”

Argento agreed, noting that “use of that term contributes to confusion rather than clarity.”

Complications Screening and Management, Psychosocial Issues

Also new in this 2026 guidance are three new sections about screening for microvascular complications, cardiovascular risk management, and management of obesity. This isn’t new guidance, but those topics weren’t included in the 2021 version because the advice didn’t differ from that of other diabetes management guidelines. However, people requested that these topics be included in the adult T1D management update, Peters said.

On the other hand, this document doesn’t cover the specifics of insulin dosing because that was covered in the 2021 version and hasn’t changed, she added.

In the 2026 update, several other sections were modified on the basis of newer information, including psychosocial care, diabetes self-management education, exercise, and nutrition.

Argento said he thought it “was a good idea to add the need for screening for micro- and macrovascular complications.”

In addition, “adding information on cardiovascular risk management was great because this is the leading cause of death in those with T1D, which is often not appreciated,” he said. “I also applaud the addition of managing obesity in T1D.”

Peters reported serving as a director, officer, partner, employee, advisor, consultant, or trustee for Vertex and receiving research grants from Insulet Corporation, Abbott Diabetes Care, and Zucara Therapeutics Inc. Argento declared serving on advisory boards for Convatec and Eli Lilly and Company and on the speakers bureaus for Dexcom, Tandem, Eli Lilly and Company, Novo Nordisk, and Boehringer Ingelheim.

Miriam E. Tucker is a freelance journalist based in the Washington, DC, area. She is a regular contributor to Medscape, with other work appearing in the Washington Post, NPR’s Shots blog, and Diatribe. She is on X @MiriamETucker and BlueSky @miriametucker.bsky.social