Nearly Half of People With Diabetes Don’t Know They Have It

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On September 17, 2025

A new global study found that nearly half the people with diabetes don’t know it, and that younger people are more likely to be unaware and undiagnosed.

In the United States, the numbers are better than the worldwide average — researchers estimated that about 1 in 6 of Americans with diabetes (17 percent) don’t know they have the condition.

Although the United States is doing better than the global average, there’s still a gap in diagnosis, says the study’s first author, Lauryn Stafford, a researcher at the Institute for Health Metrics and Evaluation at the University of Washington in Seattle.

“Given the larger uninsured population in the United States compared to other high-income countries, it is likely that this factor plays a bigger role in undiagnosed diabetes in the U.S. Young adults in the U.S., as in the rest of the world, were most likely to be unaware of their diabetes,” says Stafford.

Globally, 44 Percent of People With Diabetes Are Unaware

Using the Global Burden of Disease program, researchers pulled data from nationally representative surveys, published studies, and unpublished ones in 204 countries and territories from 2000 through 2023.

For each place, year, age group, and sex, they estimated the share of people with diabetes who are:

Undiagnosed
Diagnosed but not treated
Treated (defined as currently taking insulin or other medicines that lower blood sugar) but not at target
Treated and at target

The majority of the people reported on in the study had type 2 diabetes.

Researchers found that in 2023, only about 56 percent of people with diabetes worldwide had been formally diagnosed.

That means an estimated 248 million people had the disease but didn’t know it. In the United States, about 8 in 10 people with diabetes have been diagnosed, which is among the highest rates globally.

Worldwide, the study found that only about 40 percent of people with treated diabetes were getting optimal results and lowering their blood sugar. In addition to lifestyle changes, treatments include insulin, metformin, and newer medications like GLP-1s.

Younger People Are More Likely to Be Unaware of Their Diabetes

The findings showed that younger people were the most likely to go undiagnosed. Globally, only 1 in 5 people younger than 35 were aware they had diabetes, says Stafford.

Although the rate of undiagnosed diabetes is higher in younger people, they also have lower prevalence of diabetes compared with older adults, says Sun Kim, MD, an endocrinologist and an associate professor of medicine at Stanford University Medical Center in California.

In the United States, it’s estimated that about 3.6 percent of people ages 20 to 39 have diabetes, and about 1 in 3 of those people are undiagnosed, says Dr. Kim, who wasn’t involved in the study.

Why Are So Many People With Diabetes Undiagnosed?

There are a few reasons why people may be living with diabetes and not know it, says Stafford.

Compared with older adults, younger people are less likely to have regular checkups and get screened. That means they often go undiagnosed until complications show up. That’s especially concerning because developing type 2 diabetes at a younger age is linked to more serious complications over time.

Diabetes complications can include blindness, need for amputations, end-stage kidney disease, heart attacks, and strokes, says Kim.

Some People With Diabetes May Have No Symptoms

“Unfortunately, people with mild elevations in blood glucose [blood sugar] may be asymptomatic, which is the reason so many are undiagnosed,” says Kim.

As blood glucose increases, symptoms worsen and may include:

Thirst
Frequent urination
Blurred vision
Fatigue

“Infections, such as vaginal yeast infection, can be common,” Kim says.

The Risks of Undiagnosed Diabetes

Untreated diabetes can damage the body slowly but seriously. Over time, high blood sugar can harm the kidneys, nerves, liver, and eyes, says Kim. “Diabetes also increases risk for stroke, dementia, and certain cancers,” she says.

“Diagnosing diabetes early is important because it allows for timely management to prevent or delay long-term complications,” says Rita Kalyani, MD, the chief scientific and medical officer at the American Diabetes Association.

Lifestyle changes like eating a balanced diet, exercising regularly, and managing weight along with medications (if needed) can keep blood sugar in check and help prevent complications.

Why Screening Matters

The American Diabetes Association recommends that all adults start regular diabetes screening at age 35, even if they don’t have risk factors.

People who are overweight or have obesity with one or more risk factors (such as high blood pressure or family history) should start getting screened at an earlier age, says Kim. For people of Asian ancestry, she notes, the criteria for overweight and obesity begin at lower weights.

Whether or not you have risk factors, Sun’s recommendation is the same: Get screened. “If possible, you should discuss your concerns with your primary care provider,” she says.