BEEEEEEP! BEEEEEP! wails the Dexcom.
Birdy, who is coloring at the kitchen table, yells back, “BEEEEEP! BEEEEEEP! Mawm, your Dexcom is making the beep sound again,” and she absently points her red crayon towards the bottle of glucose tabs on the table nearby.
For the most part, I can rely on the Dexcom to be accurate when it’s throwing out results to me. Low alarms are ones that I take very seriously, as well as the double-down arrow alarms, because they need immediate action. My blood sugars tumble fast once they’re under 70 mg/dL, so when the CGM hollers to warn me of an “UNDER 65 mg/dL,” I can pretty much guarantee that the “LOW” alarm is the next one on tap. High alarms are also taken seriously, but not with the same immediacy. I will finish driving somewhere before correcting the high, whereas a low makes me pull the car over and treat.
Point is, I trust the CGM. A lot. More than the FDA and the owner’s manual says I should (no, I don’t always test to confirm a low because I’d rather take the chance of the CGM being slightly off than take the chance of face-planting in the backyard). While the data was overwhelming at first, I’ve come to rely on it, and it helps shape my diabetes decisions throughout the day. My health is – dare I say? – better as a result of wearing a second, sometimes clunky-ass device.
But when it’s wrong? I’m tweaked out and frustrated, spoiled by the accuracy and precision I’ve come to expect from the sensor.
Yesterday morning was Dexcom Replacement Morning (i.e. the installation of a new sensor, peeling off the week-old Toughpad/transmitter combination that looks and feels as if I’m removing a 90 yr old skin graft after so many days stuck to my thigh), so I knew that the receiver data might be a little off for a few hours (seems to be standard for me). However, by the time I went to the gym that night, I’d been wearing the sensor for at least seven hours, and had calibrated it three times. My meter said 217 mg/dL before walking into the gym, and the Dexcom confirmed the same range, in an ish-y sort of way, with a 250 mg/dL.
Since my blood sugar was high and I was feeling sluggish, I opted for the stationary bike instead of a treadmill run, and after the first 3 minutes, I noticed that the Dexcom was trending down. But not crazy-down. More like comfortable, exercise-expected down, with a 190 mg/dL and a southeast-facing arrow.
About fifteen minutes later, I noticed that I was sweating a lot. More than usual. And it wasn’t “workout sweat,” which seems to come in at a steady pace. This sweat felt pulsing, like it was a flash flood of panic, and within a few minutes, my forehead was slick and even my elbows were damp. The Dexcom said I was 200-and-something with double-down arrows, but my body was sending me an entirely different message. Which is why I wasn’t surprised to see a 70 mg/dL on my meter.
Lips numb and counting out five cherry glucose tabs from the jar (putting them all in my mouth at once while I was counting, and then realizing I should probably eat them one at a time), the low wasn’t quick to give in to the sugar onslaught, giving me plenty of time to question my trust of the CGM. I don’t want to consider the Dex “only as good as it’s last result,” but missing a low by almost 150 points has shaken my confidence in this particular sensor’s accuracy.
My Dexcom is like the little girl with the curl on her forehead: When she was good, she was very good, but when she was bad, she was horrid. Thankfully, I get more good than horrid, but it will take me a few days to regain trust. In the meantime, I’m leaving a trail of extra test strips in my wake.