Medicare’s expansion of coverage for A1c for diabetes screening in 2024 was followed by significant increases in use of the test and detection of prediabetes, new data showed. 

“This is the first study I’m aware of that specifically looks at how the testing patterns changed after Medicare adopted the rule,” said co-investigator Jason Ng, MD, clinical professor of medicine in the Division of Endocrinology and Metabolism at the University of Pittsburgh Medical Center in Pittsburgh.

The magnitude of the increase in people with detected prediabetes was somewhat surprising, he told Medscape Medical News.

“I expected more people to take advantage of it, but I didn’t expect it to increase as much as it did.”

Before January 1, 2024, Medicare covered only an oral glucose tolerance test or fasting blood glucose for diabetes screening. On that date, the Centers for Medicare & Medicaid Services (CMS) expanded coverage to include A1c, which is often preferred because it does not require fasting or lengthy visits. A1c can also detect dysglycemia that fasting glucose testing may miss in people aged 60 years and older.

Ng and colleagues presented the findings in a late-breaking poster at the American Diabetes Association (ADA) 2026 Scientific Sessions.

Increased Use of A1c Testing

The researchers compared laboratory data from Quest Diagnostics from January 1, 2022, to September 30, 2023, with data from the same period in 2024-2025.

Mean monthly A1c testing volume among people aged 65 years and older increased from 418,532 to 544,389 after Medicare expanded coverage, a 30.1% increase (P < .0001). This suggested “awareness of the addition of [A1c] testing to Medicare-covered diabetes screening tests,” the authors wrote in the poster.

Before the coverage expansion, 48.5% of A1c screening tests resulted in a prediabetes or diabetes diagnosis vs 67.4% afterward. Detection of prediabetes rose from 37.3% to 54.7%, whereas detection of type 2 diabetes increased just slightly, from 11.2% to 12.7%.

Glucose-only screening may underdiagnose prediabetes in older adults; therefore, screening with A1c “may capture a population that was previously missed,” the authors noted. They acknowledged, however, that data suggested only a small proportion of older adults with A1c-defined prediabetes would progress to diabetes.

The findings were encouraging, Ng said. Identifying people with prediabetes — or even diabetes — earlier could allow clinicians to intervene sooner with appropriate medications, such as metformin, or education about lifestyle changes, healthy eating, and exercise to help prevent disease progression, he explained.

Physicians Requested A1c Coverage for Years 

Asked to comment, Kate Kirley, MD, former vice president of prevention solutions at the American Medical Association (AMA) and now a private consultant, said expanded Medicare coverage has been long sought. 

“I used to speak with physicians across the country, and they were asking for Medicare coverage of A1c screening for years,” she told Medscape Medical News. “I think there was pretty quick awareness when it happened.”

Kirley, whose title at AMA in 2024 was director of chronic disease prevention and programs, called it a “great study” but noted its limitations.

“We don’t know a lot about why the individuals are receiving the A1c test. It does look like they tried to exclude people who already had diabetes, but I’m not clear on how good that exclusion is if you’re just looking at Quest data,” she said. “But it is very interesting that this high percentage are showing a prediabetes result.”

Although the laboratory data did not address subsequent care, “I think it is reasonable to say that there’s an increased likelihood that people are having their prediabetes addressed,” she added.

One important option for addressing prediabetes, and an impetus for the coverage change, was the Medicare Diabetes Prevention Program (MDPP), a lifestyle coaching program covered under Medicare Part B for eligible beneficiaries with prediabetes. The MDPP had previously accepted people screened using A1c results despite Medicare’s lack of coverage for the test itself, Kirley said.

“I think what pushed them over the edge was the fact that the MDPP did include it as criteria,” Kirley said, adding that the Biden administration had also been concerned about inequities because commercially insured patients could obtain A1c testing for screening purposes, whereas Medicare beneficiaries could not. 

The MDPP remained underused, in part because of Medicare reimbursement issues, so access could continue to be a challenge for “people who would be eligible to participate,” she noted. Nonetheless, clinicians “absolutely” could consider referring patients with prediabetes to an MDPP when available or to a diabetes prevention program more generally. 

Like Ng, Kirley also cited metformin and newer therapies such as GLP-1 receptor agonists as valuable options for patients with prediabetes at risk of developing type 2 diabetes. 

Medscape Medical News reached out to CMS for comment, but the agency did not respond by the deadline.

The study was funded by Quest Diagnostics. Ng and Kirley reported having no relevant disclosures.

Miriam E. Tucker is a freelance journalist based in the Washington, DC area. She is a regular contributor to Medscape, with other work appearing in the Washington Post, NPR’s Shots blog, and Diatribe. She is on X @MiriamETucker and BlueSky @miriametucker.bsky.social.