Continuous Glucose Monitors (CGMs) are gaining traction in the nutrition world and for a good reason – read my blog here to learn why. This week I trialled a new type of CGM called Dexcom G6. This blog compares the Dexcom against my usual ‘go-to’ Freestyle Libre CGM. Overall I prefer Freestyle Libre due to its overall ‘ease of use’. Dexcom was definitely good and I loved that it could be hidden by wearing it on the stomach, but overall the experience was less intuitive and the data harder to analyse.
A) GETTING STARTED
Putting the sensor on: Inserting the Dexcom was arduous. First step was to attach a patch to my body using a large sensor device. This patch has the filament that goes into your body. Second step was to insert a transmitter into the patch. The transmitter is like an old-school bank security device. Third step was to put an ‘overpatch’, like a plaster/Bandaid, over the top to stick the edges down and keep it tidy. Because this wasn’t mentioned in the instructions I didn’t do it until the day before I was due to take the sensor off. Also the kit did not come with an alcohol swab, despite the instructions stressing the importance of cleaning the site before insertion. This meant I didn’t use an alcohol swab – who has swabs lying around the house? – which made me worry. Not because I was seriously concerned, but I’m someone who likes to follow instructions and this bothered me. It wouldn’t have cost the manufacturer much to get the swab included so it felt like an unnecessary but frustrating oversight.
By contrast the Freestyle Libre is inserted in one action (patch, transmitter and overpatch) and you’re done. The kit includes a swab too.
The Dexcom G6 was downright painful for me for about 15 minutes and I was certainly very aware of it for the first 24 hours. This may be because of where I put the sensor (perhaps a bit low) and their customer support said this could happen if you hit a nerve. On taking the sensor out the filament that goes into your body was distinctly longer (say 7mm) than the Freestyle (5mm). Maybe this explains the extra pain, or maybe I was unlucky. Either way I’m not rushing to wear another one. After the first 15 minutes it hurt a bit in the first day or two. After that, I barely noticed it was there.
B) USING THE MONITOR
Appearance: Overall the Dexcom sensor was around 5cm x 2.5cm and was nicely hidden under my clothes (worn on my tummy). The size of it and the transmitter-bank-security thing did make me feel like a bionic human. By contrast the Freestyle libre measured roughly 2.5cm by 2.5cm, but was worn on the back of my upper arm for everyone to see. I didn’t like the sensor being visible so I preferred using Freestyle during the winter months when my arm was covered.
Transmitting data for analysis: Both CGMs have simple apps that are easy to set up. The Freestyle Libre requires the phone to be held to the device to get an immediate reading and it pulls-down the last 8 hours worth of data. The Dexcom transmits data continuously without needing to hold up the phone. This made it slightly easier to use. I did find however that the Bluetooth wireless connection was a bit sketchy at times so often I couldn’t get a reading. (This did happen sometimes with Freestyle too – but less frequently). Also the Dexcom only pulled-down data from the last 3 hours and it didn’t have great connection when I was lying on my side in bed so I got very little overnight data. This was an issue for me because I don’t like to leave my phone on overnight (I use aeroplane mode). Over the 10 days I managed to get only two sets of overnight data. With the Freestyle, provided I did a reading immediately on waking up I would have almost all of my sleep data capturing the previous 8 hours.
Accuracy of the data: again Freestyle wins here. In the first few days Dexcom had some significant ‘off’ readings. This eased up over time, but I calibrated several times to a blood prick glucose reader throughout the 10 days and the numbers were often wrong by 0.5 to 1.5 nmol/L - sometimes higher and sometimes lower. Freestyle has always been accurate when I have calibrated.
C) ANALYSING THE DATA
Reading the data as it arrives on the App: Freestyle allows you to set the low and high of the main screen and operates in a portrait orientation so that you get a ‘peakier’ graph that makes sudden excursions of blood glucose look a bit more like a ‘health alert’ or a warning that a food/meal may not have been ideal. The Dexcom app has a low of 2 and high of 16 as the main screen and operates in landscape. So that it is harder to see and analyse data if you a non-diabetic because most of your glycaemic movement is in the ‘healthy range’ keeping the graph relatively flat.
More detailed analysis: The Dexcom comes with an option of transferring data to another app called Clarity where you get detailed reports of your data. You choose the report you want and then download it. This is great, but a little cumbersome. The reports take up to 5 seconds to download (which is slow in our modern world) and the graphs, on the small phone screen, need a lot of scrolling in and out to look at them. Freestyle doesn’t offer this level of interpretation. The reports are still a little flat to make them super-interesting for non-diabetics.
Saving the data: It was very easy to download the reports of interest from Dexcom Clarity and save them to my computer. Freestyle however only keeps data for 3 months, after which it deletes everything without warning. My experience with Freestyle is that it is best to screenshot data and write meals/foods using photo editing software for later analysis. This is cumbersome. I’m not sure when Dexcom deletes the data if you forget to download the reports to your computer. Overall Dexcom wins on the downloading of data feature.
D) PRICE
Dexcom G6 retails at $750 for 3 x 10 days of sensors, including a transmitter device. After that 3x10 days of sensors are $350 and you don’t need to buy the transmitter again. Freestyle libre retails for around $120 for 14 days. This makes Freestyle significantly cheaper for a first time user and still cheaper for a returning user (who already has a transmitter).
CONCLUSION
Overall part of me wonders if the poor positioning of the sensor (a bit low) explains many of the issues I had with Dexcom. From speaking to other people who use CGMs they generally give Dexcom a thumbs up.
My experience is far from ‘the answer’ – it is just one users experience. But I hope you have found it interesting nonetheless.
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