Andrew @DT1Lada I agree with what you have written and suggest that many users will benefit from your words, along with the caveat that each user must determine for her/himself which location provides the more accurate readings. For instance, I’ve found the arm to be less favorable than other locations because my favored sleeping positions bring on too many “compression” faults. I always validate Sensor Accuracy with laboratory calculated readings.
Another question for discussion, knowing that there are differences between body glucose levels and blood glucose levels is “which is more important”. For instance, we all have experienced excess blood sugars, that BG above the renal threshold, being safely voided from the body. For me, a question I’ve presented to professionals, “should I be more concerned with the glucose, as evidenced by the sensor, being retained where it could do harm to my body organs”. I lean toward adjusting insulin levels to maintain proper BGL [Body Glucose Level] rather than Blood Glucose.
Firstly, I agree with you on site location. The sites I mentioned either work or don’t work for me and everyone has to find their own spot. Regarding the BG or SG levels, it is my understanding that at the extremes the sensor is challenged. I was told that when you are hyper and approaching DKA that dehydration will inhibit the free transfer of glucose from the blood to the interstitial fluid. The extreme levels of the BG will withdraw water from much of the interstitial areas due to osmosis (I think). For a while, I wondered why they measure the BG from the artery and they said “it’s a more accurate measure of the body’s metabolic state”. Thank goodness we can normally rely on the SG and BG with a fingerprick!
Since I’m the one who said those words, I feel the need to respond.
Yes, I’m well aware of the difference between SG and BG values. I’ve been diabetic over 30 years. I remember when they first introduced BG meters that could use blood from other sites, and all the caveats that they didn’t want to include in the promotional materials. It’s much different reading interstitial fluid than it is reading capillary blood from the fingertips. Even blood from the forearm is less accurate than fingertip blood. I’ve explained in other threads how interstitial fluid lags behind BG values, and why.
(Also, for the record, I studied biomechanical engineering at MIT with the intent of going into medical equipment design. In 1999 I was sitting around with my friends in my dorm kicking around plans for a closed loop pump based on information about the development of a material across campus that they hoped would make CGMs finally possible.)
All of which is precisely why (especially after having used the Medtronic Guardian 3 sensor for 2 years) I was really impressed by how consistently accurate my Dexcom has been. Whenever I’ve checked it against my BG value, it’s been closer than it has any right to be.
@WearsHats I wasn’t referring specifically to you. The “spot on” comment is used often, mainly by Dexcom users to complain about the accuracy of Medtronic CGMs. Unfortunately, the pump model, transmitter, and specific sensor are crucial components of sensor accuracy. For example, the 640g/Enlite didn’t work and the 640g/sensor3 wasn’t much better. The 670g/Sensor3 was ok but the 770g/780g GL3 transmitter/Sensor3 works as well as the Dexcom aside from the calibrations required. The 780g/G4 transmitter and Sensor 4 work wonders together without calibration.
I’d have expected the pump to make minimal difference in that, though. It’s the quality of the sensor itself that makes the most difference. And the readings are taken and processed by the transmitter, not the receiver. Medtronic did update the algorithm in the transmitter a couple of years ago, but the only way to do it was to completely replace the transmitter because only Medtronic has the equipment to update the transmitter firmware.