Continuous Glucose Monitors May Not Be Accurate for Those Without Diabetes: Study

Researchers indicate blood sugar levels in those without diabetes fluctuate significantly throughout the day, which do not lead to long-term changes in HbA1c.

New research warns that continuous glucose monitors (CGMs) may not accurately reflect blood sugar changes among individuals with prediabetes, or those without diabetes.

The popularity of continuous glucose monitors has exploded in recent years with the health conscious and athletes alike using them to track their blood sugar metrics. However, the glucose monitors offer little benefit to people who do not have diabetes, according to findings published in the journal Diabetes Technology & Therapeutics on October 1.

CGMs help people track blood sugar changes in real-time. They include small devices that an individual can attach to the back of their arm, which sends repeated signals about blood sugar to a monitor or app.

Originally approved by the U.S. Food and Drug Administration (FDA) in the mid-2000s for diabetics, the devices were approved for over the counter (OTC) use for anyone in 2024. As a result, people without diabetes have adopted using the devices.

However, using an over the counter glucose monitor can pose some risks, experts say. Since they are generally meant for people with diabetes, they can lead people who do not have diabetes to make decisions based on data that does not offer a full picture of their health, in addition to potentially causing interference, skin irritation, pain and infections.

Researchers from Harvard Medical School and Mass General Brigham’s Department of Medicine at Brigham’s Women’s Hospital analyzed data from nearly 1,000 people participating in the Artificial Intelligence/Machine Learning Consortium to Advance Health Equity and Researcher Diversity program. 

For this program, participants at the University of Alabama, University of California, San Diego, and the University of Washington wore a Dexcom G6 CGM, which measured blood sugar every five minutes for up to 10 days, starting in 2022.

Led by Dr. Jorge A. Rodriguez, researchers measured HbA1c at the start of the study and compared that to eight different CGM metrics. HbA1c is a measure doctors take to see how well the body controls blood sugar over several months. It is considered the gold standard measurement for blood sugar control.

The metrics included average blood sugar, time spent in healthy blood sugar range, and measures of blood sugar variability. The study included 412 people with type 2 diabetes, 319 with pre-diabetes, and 232 with normal blood sugar levels.

The data showed continuous glucose measurements were on par with HbA1c measurements in people with diabetes. However, among people with pre-diabetes the link between HbA1c and other metrics was much weaker. In people with normal blood sugar, the measurements had no correlation to the HbA1c measurement at all.

The researchers noted that among people with normal blood sugar, short-term fluctuations in blood sugar happen naturally with meals and activity. According to the new data, the fluctuations in people without diabetes do not lead to long-term changes to HbA1c.

As a result, researchers concluded that continuous glucose monitors are great devices for monitoring diabetes, yet do not offer the same benefits for individuals who have normal blood sugar or pre-diabetes. Instead, they may be better suited to offer real-time information about lifestyle, which can include details like how the body responds when meals are skipped or when a person is dehydrated, researchers said. The team determined that the general public should be careful about drawing blood sugar conclusions from CGM data if they do not have diabetes.

Additionally, researchers indicated that there need to be long-term studies to determine if glucose monitors can help identify people with normal HbA1c who might be at risk of developing diabetes in the future.

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