This is how easy the Freestyle Libre Flash Glucose Monitor from Abbott is to insert.
Recently I conducted a device trial comparing my Dexcom G4 continuous glucose meter to a new flash glucose meter called the Freestsyle Libre from Abbott (currently only available in Europe and the UK). They call it “flash” because you don’t see where your blood sugar is until you scan the sensor with what’s called a reader, but for my trial, it didn’t matter.
The Freestyle Libre is very popular – it was out of stock for 3 months after its release. Here is where having a Dutch sister in law who lives in the Netherlands comes in especially handy. But I should tell you the trial made me wonder: how do we know how much we can trust our devices?
I wore both the Dexcom and Freestyle for a week. Dexcom’s sensors are approved for 7 day wear. The Freestyle Libre’s for 14 days. Here at a glance are the dominant feature differences between the two.
|Features||Dexcom G4 CGM||Freestyle Libre FGM|
|Sensor approved for wear||7 days||14 days|
|Calibration||2 x day||None|
|Range||20 Feet||Not appropriate|
|Body location||Stomach||Back of upper arm|
|Sensor size||Somewhat bulky||Thin|
The Freestyle Libre pretty consistently gave me blood sugar numbers 20-30 points lower than my Dexcom. It was unnerving. I emailed a friend in Sweden who has also used both and he reported similar results with a comment, “The worst part is how do you know which to trust?”
Make no mistake, I would love Freestyle’s 14 days of not having to prick your fingers since the Freestyle Libre requires no calibration. But without calibration is it really reading where I am correctly?
My Dexcom is on the left. The Freestyle reader in the middle. Since it has the European system of mmol/l, 6.6 mmol/l as you see on the screen, is equivalent to 119 mg/dl. My meter is on the right. At 119 the Freestyle is way below my meter and Dexcom.
Over the years I’ve learned the numbers on your meter are not precise. They’re an approximate of where your blood sugar is. If you check your blood sugar two times in a row you’ll usually get two different numbers. Sometimes they’re close, sometimes not.
I also know continuous glucose monitors are measuring glucose from interstitial fluid, not blood. As such, their numbers lag about ten minutes behind your blood sugar meter reading and sometimes when your blood sugar is going up or down quickly they get a little confused.
All that said, it’s disconcerting when two devices are giving such a different reading. Abbott hopes to make the Freestyle Libre available in the US next year. And I’d love to use a glucose monitor that’s as comfortable and finger stick free as Abbott’s. I just want to know can I trust it?
Just as we keep fighting for greater meter accuracy, a twenty five point spread between two glucose monitoring devices is just too much.
For more on this and the emotional cost of devices, see my Huffington Post article here.