How accurate are Continuous Glucose Monitoring Devices?
I compared more than 80 CGM sensor readings with finger prick blood glucose readings taken at the same time. I found that the sensor readings are higher than the finger prick readings by about 1/3. One day the sensor showed 85 mg/dl and I walked to a restaurant for a meal. Halfway through I fainted due to low blood sugar level which may have been about 63. BE AWARE OF THIS ERROR WHEN USING A CGM!
, I really appreciate you sharing this information for others in the community also using a CGM or considering the use of one. Just curious, have you also brought this to the attention of your doctor and/or pharmacist and if they had any added thoughts or insight? Your post reminded me of this article, https://type2diabetes.com/living/fighting-cold, where a person was sharing a very large difference in finger prick blood sugar vs. CGM sensor readings when sick. Thanks again for sharing your experiences. Best, Minel (Team Member)
It is important to remember/realize that the CGMs (Continuous Glucose Monitors) and BGMs (Blood Glucose Monitors) test in two different ways. BGMs test blood from capillaries. CGMs test interstitial fluids.
Also, if two different BGMs test from blood from the same finger stick, the readings may be different.
The FDA controls the formula and procedures for accuracy testing before approving a device for the market in the United States.
And most CGMs have a procedure for calibrating their sensors.
Here's Dexcoms
https://www.dexcom.com/faqs/is-my-dexcom-sensor-accurate
Never take any device's reading as gospel. Be aware of their limitations and idiosyncrasies. Always listen to your body. That's where you live. It will tell you when something is "off".
Good Luck 😀))))
Great points! There is certainly a learning curve with CGMs and each one is different. So important to learn how to properly calibrate them and as you said, be aware of potential limitations. In addition to speaking with one's doctor, this is a great article on CGMs others in our community may find helpful: https://type2diabetes.com/living-with-t2d/continuous-glucose-monitoring, Best, Kelly, Type2diabetes.com Community Moderator
To my surprise my Endocrinologist told me the CGM always reads lower values than a real blood glucose monitor. My experience was it was the revers.
Interesting! It's my experience that they are all different. Ha. I think it pays to familiarize yourself with your unique CGM, as it sounds like you have. Thanks for sharing. Best, Kelly, Type2diabetes.com Community Moderator
I compared 80 sensor readings with 80 blood glucose readings taken at the same time on 6 different sensors. I found only 2 where the sensor was higher. The average difference was blood glucose reading is 0.826 times the sensor reading.
