People with diabetes in the United States and several other countries do not get effective treatment to control their disease, U.S. researchers said on Tuesday, and health insurance, not personal wealth, plays a big role in determining which diabetics get good care.

The findings suggest millions of people with diabetes are undiagnosed or poorly treated, putting them at risk of an early death from heart disease or significant complications of diabetes, such as blindness, chronic kidney disease and foot problems that can require amputations.

“Too many people are not being properly diagnosed with diabetes and related cardiovascular risk factors. Those who are diagnosed aren’t being effectively treated,” Dr. Stephen Lim of The Institute for Health Metrics and Evaluation at the University of Washington in Seattle said in a statement.

“This is a huge missed opportunity to lower the burden of disease in both rich and poor countries,” said Lim, who worked on the study published in the Bulletin of the World Health Organization.

Diabetes is reaching epidemic levels. An estimated 280 million people, or 6.4 percent of the world’s population, are suffering from it, according to the researchers.

Overweight people have an increased risk of developing it, and cases are predicted to rise swiftly in coming decades as obesity rates increase.

The research team used data from national health surveys to study diabetes diagnosis and treatment rates in the Colombia, England, Iran, Mexico, Scotland, Thailand and the United States and found widespread rates of undiagnosed and poorly treated diabetes.

In the United States, nearly 90 percent of adult diabetics - or more than 16 million adults aged 35 and older - fail to meet widely accepted targets for healthy levels of blood sugar, blood pressure and cholesterol.

In Mexico, 99 percent of adult diabetics are not meeting those targets.

In Thailand, up to 62 percent or more than 663,000 men surveyed are either undiagnosed or untreated for diabetes.