To Calibrate or Not To Calibrate?
There is no question that continuous glucose monitoring (CGM) systems have been one of the most transformative technologies in diabetes. This technology has evolved to the point where most believe it is now the standard for glucose measurement. This is why I find it amusing that many CGM users still calibrate or check their system with an old-fashioned finger stick. What’s more amusing or perhaps ironic is the CGM is actually MORE accurate and MORE reliable than these old systems.
Not One Man's Opinion
This is not an opinion, it’s a statement of fact based on all available data. Now I realize that I am in a somewhat unique position given my other site Diabetic Investor, which allows me access to some of the smartest people on the planet. So, to put this in perspective everyone can understand let’s go way back when conventional finger stick monitors ruled the world and CGM wasn’t even in development.
Is Diabetes 20% Wrong?
Way back then the FDA held a meeting about improving the accuracy of finger stick glucose monitors, most patients didn’t know and likely still do not know is that conventional finger stick meters can deliver a result that is 20% inaccurate. To put this into perspective, if your blood sugar reads, let’s say 200 mg/dl, this really can indicate a blood sugar anywhere between 160 -240. That obviously, is a fairly significant range, and could potentially influence dosing decisions. Now this variance is different from meter to meter and can even vary from one box of test strips to the next. The point is, the result shown may or may not indicate a “real” glucose level.
The reality is CGM systems are actually MORE accurate than a conventional finger stick meter as cgms are governed with a tighter inaccuracy range somewhere around 8% or 9%. This is the reason I do not personally calibrate my Dexcom sensor. Ever. But, there are other reasons as well:
- I am not concerned with what my numbers are at any one point in time. I am concerned with what my glucose trends are and if I am staying in range. To me, Time in Range is a more important metric than any one number. This isn’t so for all patients, but it is for me.
- Based on my knowledge of glucose monitoring, it does not make sense to calibrate an accurate technology using an inaccurate technology.
- I no longer even own a conventional finger stick meter and after years of sticking my fingers, I am delighted that I will never own one again in my lifetime.
As a Type 1 patient, I use a plethora of technology. I am currently on the OmniPod 5 system which incorporates my Dexcom G6 sensor. Way back in the day, my first insulin pump was a MiniMed 508 and along the way I have used the Tandem Basal IQ. I’ve settled on the OmniPod because I like to be tubeless! I have also accepted the fact that NO technology is ever perfect and these technologies being medical devices can and do fail from time to time.
Diabetes technology has become part of my life just as my smartphone has become part of my life. And just as there are times when my smartphone has no service there are times when my diabetes technology does not perform to perfection. Do I like it when it happens? No, but it comes with the territory of managing the unknowns of diabetes.