After my A1C test revealed prediabetes, I was determined to take steps to avoid the damaging effects of high blood sugar, including kidney disease, heart disease, and vision loss. I was unsure what to do, since I’m average weight, eat a healthy diet, and exercise regularly. I didn’t want to randomly experiment, then wait for my next A1C test to reveal whether my actions had made a difference. I needed to know how my behavior impacted my blood sugar.
Luckily, this information is provided by a continuous glucose monitor (CGM), a quarter-sized disk worn on the back of the upper arm. CGMs are only approved by the US Food and Drug Administration for use by people with diabetes, and they require a prescription to purchase. While Medicare and most insurance programs won’t cover CGMs for people with prediabetes, some experts say CGMs are helpful for those at risk of diabetes. Eugene E. Wright, Jr., a doctor and medical director of performance improvement at the South Piedmont Area Health Education Center in Charlotte, North Carolina, agrees. “CGMs are very useful for people with prediabetes, since diabetes complications can be reduced with early diagnosis and treatment,” he says. He adds that “research shows the benefits of early and aggressive treatment can last for 40-plus years.”
I selected four CGMs that are widely available, reasonably priced, easily applied, and use a smart phone as a transmitter: Abbott FreeStyle Libre 2, Abbott FreeStyle Libre 3, Dexcom G-7, and Nutrisense.
Several popular CGMs aren’t covered in this review. I didn’t try the Eversense implanted device, but this may be a good option for those who need a sensor lasting six months. The Medtronic Guardian Connect and Eversense must be calibrated with daily fingerstick calibration, so I didn’t try those either. I also didn’t address factors important to users with specific needs (such as insulin pump compatibility, approval for use by children, etc.). While this is not an issue for many users, all CGMs measure “interstitial” glucose rather than blood glucose. Therefore, those using finger stick glucose to check CGM readings may find discrepancies in readings when blood glucose is rapidly changing.