Type 5 Diabetes May Affect Up To 25 Million People. Critics Say The Evidence Is Still Thin

Lean, Young Patients Who Fit Neither Type 1 Nor Type 2 Now Have A Diagnosis

In the early 1950s, a British physician running a diabetes clinic near Kingston, Jamaica, met 13 patients who fit neither of the two diabetes types doctors recognized at the time, NPR reported. They were young and thin, according to an NPR report, yet none developed ketoacidosis, a dangerous buildup of acid in the blood and a common symptom of type 1 diabetes.

More than 70 years later, the International Diabetes Federation gave that pattern its own name: type 5 diabetes. Supporters call the recognition long overdue, while critics say the evidence does not yet justify a new category.

Why Is Type 5 Diabetes Being Recognized Now?

Newer metabolic studies and an international expert meeting led the IDF to give a long-reported pattern its own name, though critics say the case is not settled.

Doctors have known of the pattern for decades. Philip Hugh-Jones described it in a 1955 report from Jamaica in The Lancet, and the World Health Organization (WHO) added malnutrition-related diabetes to its classification in 1985. WHO removed the category in 1999 amid disagreement over whether undernutrition alone was enough to cause this form of diabetes, according to a consensus statement (a document laying out what a panel of experts agrees on) published in October 2025 in The Lancet Global Health.

Cases kept surfacing in low- and middle-income countries, including Bangladesh, Ethiopia, India, Nigeria and Uganda, a 2022 paper in Diabetes Care noted. In January 2025, experts gathered in Vellore, India, and proposed the name type 5 diabetes, the consensus statement says. Type 5 was chosen because efforts were already underway to label other forms of diabetes as types 3 and 4, which left 5 unclaimed, NPR reported. At its World Diabetes Congress in Bangkok that April, the IDF formalized the name and launched a working group to write diagnostic criteria and treatment guidelines.

Authors of the consensus statement write that emerging evidence strongly supports a distinct category, and they call on the wider diabetes community to recognize it. Advocates are also pressing other bodies, including WHO, to follow, NPR reported.

Albert Einstein College of Medicine’s Global Diabetes Institute, whose director, Meredith Hawkins, chairs the IDF working group, estimates that type 5 diabetes affects 20 million to 25 million people worldwide. In its own announcement, the IDF repeats the figure, placing cases mostly in regions such as Asia and Africa among lean, undernourished teens and young adults.

How Is It Different From Other Forms?

Type 5 involves too little insulin, normal sensitivity to the insulin that is made, and none of the antibodies that mark the autoimmune attack behind type 1.

In type 1 diabetes, the immune system destroys the pancreas cells that make insulin. In type 2, the body struggles to use the insulin it makes, a problem called insulin resistance, the IDF explains. People with type 5 diabetes can make some insulin, and their cells respond to it, but they cannot make quite enough to keep blood sugar in check, NPR reported.

Per the consensus statement’s abstract, patients are lean and young (a body mass index below 18.5 and an age under 30), with a major shortfall in the insulin the pancreas releases, normal insulin sensitivity in the liver and the rest of the body, no ketoacidosis and no islet cell autoantibodies (immune proteins that point to an attack on insulin-making cells). Body mass index, or BMI, is a weight-for-height measure, and 18.5 is the usual cutoff for underweight.

Thinness alone does not settle the diagnosis. A 2026 review in Diabetes/Metabolism Research and Reviews says relying on BMI alone is insufficient and that accurate diagnosis requires nutrition history, metabolic features and the exclusion of inherited diabetes.

How Strong Is The Evidence For Type 5 Diabetes?

Limited. A small 2022 study offers a detailed look at the metabolism, and specialists disagree about what it proves.

Researchers at Christian Medical College Vellore in India and Albert Einstein College of Medicine in New York examined 73 Asian Indian men for a 2022 study in Diabetes Care. Twenty had diabetes with a low BMI. Fifteen others had type 1 diabetes, 13 had type 2 and 25 had no diabetes. To avoid mixing in other conditions, the team excluded men in the low-BMI group who had a history of ketoacidosis, positive antibody tests, pancreatic abnormalities on imaging or mutations in genes tied to inherited diabetes. Participants with diabetes also had their blood sugar brought under control for two weeks beforehand, so that high glucose would not skew the results.

After a standardized liquid meal, the low-BMI group released less insulin than the type 2 group and the lean men without diabetes. In clamp tests, which keep blood sugar steady while insulin is delivered, their tissues took up glucose more than twice as fast as the type 2 group’s (10.1 versus 4.2 milligrams per kilogram per minute), a sign of greater insulin sensitivity.

Because the study was cross-sectional, capturing a single point in time, and included only men, it could not establish cause and effect or show what happens in women, its authors wrote. They added that strict methods limited the sample size, and that birth weights could not be compared because most participants were born at home or in small health centers decades earlier without records. They described theirs as the first to comprehensively evaluate the condition’s metabolic profile.

According to the IDF, the condition is believed to stem from impaired pancreatic development due to long-term nutrient deficiencies. Researchers have speculated that the insulin shortfall stems from fewer insulin-making beta cells, the 2022 paper noted, citing rodent studies in which maternal protein malnutrition left offspring with lower beta-cell mass.

A 2025 review in Diabetes & Metabolic Syndrome: Clinical Research & Reviews by Anoop Misra, Shashank Joshi and Ambrish Mithal, researchers based in India, concluded that reclassifying malnutrition-related diabetes as type 5 is presently unwarranted. They argued that low BMI is an unreliable stand-in for malnutrition in populations that are often lean by build, that the condition overlaps with other forms of diabetes, especially autoimmune ones, and that malnutrition may be more often a consequence of diabetes than a cause. They also pointed to the 2022 study’s small, male-only sample and lack of follow-up, and said falling undernutrition rates in poorer countries diminish the condition’s current relevance.

In a 2026 letter in The Lancet Global Health, Misra and colleagues added that the consensus statement leans on low BMI as a proxy for malnutrition and extrapolates from small, mixed studies. Consensus authors answered in the same journal.

What Does The Evidence Actually Support?

A useful flag for doctors and researchers, not a finished diagnostic rulebook.

Hawkins chairs the working group, and Nihal Thomas of Christian Medical College Vellore co-chairs it. Beyond writing diagnostic criteria and treatment guidelines over two years, its tasks include building a global research registry and creating education modules for health care workers. Hawkins and Thomas also helped write the 2022 study and the consensus statement.

Treatment evidence is thin. Many people with type 5 diabetes may manage with oral medication instead of insulin injections, the IDF says. Diabetes Voice, the IDF’s own publication, adds that more studies are needed to establish evidence-based treatment plans. Getting it wrong carries risk: insulin therapy can cause dangerously low blood sugar, especially for people with food insecurity, the 2022 paper noted.

Gemma Rojo Martínez, a diabetes researcher in Málaga, Spain, summarized the consensus statement’s recommendations as more research on cause, burden and natural history, evaluations of the proposed diagnostic criteria in different populations, and intervention studies to find the best treatment. She added that health systems in countries that receive migrants should know about the condition, since some migrants may have it because of poor living conditions where they came from. Diabetes Voice makes a similar point about refugees, asylum seekers and migrants who experienced childhood undernutrition and later resettled in high-income countries.

Type 5 diabetes now has a name and an international working group. Until formal criteria arrive and larger studies include women, the label is best read as a prompt to look harder at lean patients whose diabetes fits neither familiar type, and not as proof of a separate disease.

Disclaimer: This article is a roundup of reports, studies and expert commentary on type 5 diabetes and is not medical advice. None of the sources proved that undernutrition causes the condition, and the estimate of 20 million to 25 million cases is a projection, not a count. Experts disagree about whether the condition should be a separate category, and diagnostic criteria are still being written. Anyone with questions about diabetes should talk with a doctor.