Nearly half of adults with diabetes worldwide are undiagnosed, global study finds

Nearly half of adults worldwide who have diabetes are unaware of their condition, leaving millions at risk of serious complications, according to a sweeping new analysis published in The Lancet Diabetes & Endocrinology.

The study, which used data from more than 200 countries spanning 2000 to 2023, estimated that about 44% of people aged 15 and older with diabetes remain undiagnosed. Researchers evaluated how well health systems identify, treat and control diabetes by measuring the proportions of people who are undiagnosed, untreated, receiving suboptimal care or achieving optimal blood sugar control, and disaggregated those metrics by age, sex, location and year.

Among people who have been diagnosed, the analysis found that roughly 91% receive medication, but fewer than half of those treated achieve recommended blood glucose control. Taken together, the study team estimated that only about 20% of people with diabetes worldwide are effectively managing the disease.

The study identified important patterns by age and geography. Younger adults were more likely than older adults to be undiagnosed, despite the long-term risks of untreated diabetes, which include heart disease, kidney failure, blindness and nerve damage. Diagnosis rates were higher in wealthier countries such as the United States and Canada, while in lower-income regions — particularly parts of sub-Saharan Africa — fewer than one in five people with diabetes were aware of their condition.

Lead author Lauryn Stafford, a researcher at the Institute for Health Metrics and Evaluation at the University of Washington, said the findings should prompt action by governments and health systems. "By 2050, 1.3 billion people are expected to be living with diabetes, and if nearly half don’t know they have a serious and potentially deadly health condition, it could easily become a silent epidemic," Stafford said in a press release accompanying the paper.

The researchers cautioned that prescriptions alone are not enough to control blood sugar across populations. They called for stronger systems for monitoring, patient education and lifestyle support alongside medication. For some people with prediabetes, early clinical attention combined with moderate lifestyle changes can return blood glucose to a normal range and delay or prevent progression to type 2 diabetes, the study notes, citing established guidance from diabetes organizations.

A registered dietitian who was not involved in the study emphasized the value of regular health checks and diet and activity changes to reduce risk. "Many people would not have signs or symptoms until their diabetes is very advanced, and many people are not going to the doctor often or at all for lab work," Tanya Freirich, a dietitian in North Carolina, said in an interview. She recommended increasing fiber from whole, minimally processed plant foods and staying consistently active to help regulate blood sugar.

Freirich also noted limitations inherent in estimating the number of undiagnosed cases. "Those are data points that are unable to be confirmed until diagnosed," she said, adding that there may be unknown factors not included in the models used by researchers.

The study underscored the uneven progress in diabetes care over the last two decades and highlighted the potential scale of future burdens on health systems. It called for targeted screening in populations at higher risk, improved follow-up and education for people who are diagnosed, and broader public health measures to promote healthier diets and physical activity. Previous research cited by the authors has found that dietary patterns such as the Mediterranean diet, coupled with other lifestyle measures, can reduce the risk of developing type 2 diabetes.

The authors said addressing diagnosis and control gaps will require coordinated efforts across primary care, public health and community settings, especially in low-resource regions where diagnostic capacity and long-term care infrastructure are limited. Policymakers and health systems seeking to blunt the projected rise in diabetes prevalence will need to balance expanded screening and treatment access with investments in patient education and lifestyle-support programs that can improve long-term outcomes.