New Form of Diabetes Recognized as Type 5, Targeting Slim Young People

Health officials have officially recognized a new form of diabetes described as type 5, a condition that appears to affect young, slim individuals who may not fit the classic profiles of type 1 or type 2.

The designation follows decades of observation, beginning in Jamaica in 1955 when Dr. Philip Hugh-Jones documented a cluster of 13 patients with signs of diabetes that did not match existing categories. The condition was later labeled 'malnutrition-related diabetes mellitus' by the World Health Organization, a label dropped in 1999 for lack of supporting evidence. Now, the International Diabetes Federation has coined the term type 5 diabetes to reflect a distinct phenotype that clinicians say is not adequately captured by current classifications.

Experts estimate roughly 25 million people globally could be living with type 5 diabetes, many of them undiagnosed, including slim teens and young adults in lower-income countries and, in some cases, individuals misdiagnosed as having type 1 diabetes. In the United States, there are no specific estimates, and the American Diabetes Association has not formally added type 5 to its disease classifications. Researchers also highlight that refugees, migrants and people with eating disorders may be at higher risk due to malnutrition, according to experts.

Symptoms of type 5 diabetes are largely similar to type 1, including increased thirst, frequent urination, headaches, blurred vision, fatigue and slow-healing cuts and sores. These signs also overlap with classic symptoms of malnutrition such as weight loss and fatigue. The Mayo Clinic notes that people with the condition are typically underweight, meaning they have a body mass index (BMI) below 18.5. By contrast, the average American has a BMI around 29, which is overweight or obese by standard measures.

Experts believe people with type 5 diabetes can produce insulin and are not resistant to it, but their pancreas is underdeveloped and cannot make enough due to malnourishment. Because of this, treating type 5 with insulin, as in type 1 or type 2, is often ineffective. Doctors are now investigating the impact of a high-protein diet rich in nutrients like zinc, B vitamins and magnesium to help patients gain weight and reduce glucose spikes. Low doses of insulin may also be used but with caution.

Earlier this year, a study published in The Lancet Diabetes & Endocrinology renewed interest in type 5 diabetes. The Young-Onset Diabetes in Sub-Saharan Africa (YODA) study sought out nearly 900 young adults diagnosed with type 1 diabetes in Cameroon, Uganda and South Africa. When researchers analyzed blood samples, roughly two in three lacked the autoimmune markers typically seen in type 1, and insulin production, while present, was lower than in type 2 diabetes. The findings suggested a distinct form of diabetes that parallels the historical observations made in the 1950s.

In a companion piece published a month later in Lancet Global Health, a team of 50 researchers from 11 countries urged the international diabetes community to recognize this distinct form and to promote more research into its phenotype, pathophysiology and treatment. They warned that misdiagnosis and underdiagnosis are likely to have negatively affected the care and lives of millions of individuals with type 5 diabetes worldwide.

Global projections indicate the number of people living with type 5 diabetes could more than double by 2050 compared with 2021, underscoring the need for clear diagnostic criteria and targeted care.

Despite rising interest, the United States has yet to adopt a formal classification for type 5. The American Diabetes Association has not issued a definitive stance, and there are no reliable U.S. estimates at this time. Some clinicians emphasize the importance of distinguishing malnutrition-driven cases in low- and middle-income countries from autoimmune or insulin-resistant diabetes seen elsewhere, to ensure appropriate treatment and monitoring.