You might be concerned if you have seen the recent headlines about continuous glucose monitors (CGMs). But you can most likely relax.
A new study made headlines saying that CGMs may not be as accurate as people believe. The worry was raised by people with healthy blood sugar who use the devices to learn how diet impacts their blood sugar. We recently wrote about the rise in popularity of CGMs for people without blood sugar concerns. This new study, with its alarming finding, used people without blood sugar concerns.
For people without blood sugar concerns, CGMs may be overestimating blood sugar levels and causing people to make unneeded diet changes. The CGMs consistently showed higher blood sugar levels than finger-prick tests. When people in the study drank whole-fruit smoothies, the CGMs overestimated the GI of the drink by 30 percent.
While the headlines are alarming, they are aimed at people without blood sugar concerns. If you have a blood sugar concern, being up to date and seeing fluctuations in your blood sugar can be more important than perfect accuracy. You most likely already know the GI of foods and do finger-prick tests.
Prof. Javier Gonzalez from the Department for Health said, “CGMs are fantastic tools for people with [blood sugar concerns] because even if a measurement isn’t perfectly accurate, it’s still better than not having a measurement at all. However, for someone with good glucose control, they can be misleading based on their current performance… We want to better identify the sources of the error in CGMs so that we can improve their performance in the future and have active research on this topic.”
CGMs can act as useful goalpost markers for people with blood sugar concerns and help them see when they are off the path. But, as we wrote in our last blog, they can give “TMI” to people without blood sugar concerns that may lead to unnecessary worry.
Moreover, this research shows that CGMs can be inaccurate for people without blood sugar concerns. However, for many people with blood sugar concerns, they can be very accurate.
The study did not include anyone with blood sugar concerns, so the devices could be more accurate for them. CGMs are calibrated for people with blood sugar concerns, meaning they are sensitive to that range. (https://www.sciencemediacentre.org/expert-reaction-to-study-looking-at-continuous-glucose-monitors-and-measuring-blood-sugar-levels-in-people-without-diabetes/) Looking for accuracy outside of that range may be causing the problem. The CGMs aren’t being used by their intended audience.
Dr. Sufyan Hussain, a blood sugar expert from King’s College London, said that CGMs are valuable for people with blood sugar concerns, but for people without them, “they can sometimes yield less reliable data – particularly if the devices are not designed or calibrated for [their blood sugar range.]”
To sum it up, this study said that CGMs aren’t accurate for people without blood sugar concerns without checking how accurate they are for people they were designed for. That is like a study saying left-handed scissors are hard to use for righties without looking at how lefties perform with them. Just because CGMs aren’t accurate for people without blood sugar concerns doesn’t mean they aren’t precise and helpful when used for their intended purpose.
