Prescription CGMs. How do they compare? Coming soon….

Prescription CGMs. How do they compare? Coming soon….
Prescription CGMs. How do they compare? Coming soon….

I’ve been lucky enough to get my hands on all three of the devices that will soon be available on prescription in England & Wales.

The Dexcom One, kindly provided by Dexcom for this test, ahead of it being directly available, the Libre2 and the Aidex (paid for rather than on prescription).

I’ll be looking at:

  • What’s in the box
  • Application
  • Wear
  • The apps
  • The analysis tools
  • The data

There will be the usual data collection, using collection points at 7, 9, 11, 13, 15, 17, 19 and 21 hours, plus specifically, if any sensor alerts low or alerts for an upcoming low, testing at that alert.

Hopefully the n=1 data will give an impression of what each of them is like to live with as well as how they compare to fingersticks.

Oh, and I’ll be running the Dexcom G6 alongside to provide the datum, just because…

If there’s anything you want to know, put it in the comments box below.

Keep your eyes peeled!

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    • Libre3 isn’t available on prescription in the UK. It requires a separate funding model, but it will be tested in the future against the G7.

  1. I am entirely on #TeamDexcom! If only it had interoperability with Medtronic insulin pumps. I love Dexcom so much, it’s driving the selection of my next pump when the warranty runs out on the current one.

  2. I think I already know your opinion of the Aidex system. From the product sheet, the Dexcom One seems in essence the same as the G6 but with slightly less capability. The Libre2 seems like it might be moving towards being a true CGM but you still need to scan to get the readings. You can’t just get the readings on your phone like a true CGM. I will be interested to read your impressions and if the MARD of 9.3% matches your experience.

    • Because, as the title states, these are the systems available on prescription in England and Wales.

      The Glucomen Day isn’t.

      I might mention it if there’s information in the packs relating to that, but as a Garmin user, it’s not a feature that’s of use to me.

      There will be a follow up to this, testing the devices that aren’t available on prescription. This will include the Glucomen Day, Libre3, Dexcom G7 and Medtrum Nano.

        • I have no idea. I’d have expected them to be on the list by now if they were. The product has been available since for two years.

      • Tim, looking forward to this. As a fellow Garmin (watch and bike computer) currently using L2 to feed them would love to hear how/if they others can do this as that’s a dealbreaker for me. Thanks for the work you do.

  3. Hi Tim,

    This ran into a bit of a list (apologies) – hope it helps rather than sending you to sleep….

    Main points for me will be Accuracy during normal BG range operation (3.9-10 mmol etc)

    Accuracy during highs and lows (particularly highs as Libre 2 seems to be a bit rubbish past 12-14.

    Graduation of readings during operation (Libre 2 can seem a bit ‘rapid rise’ and ‘rapid fall’ sometimes, rather than stepping between points over time)

    Bluetooth stack reliability – do they connect consistently to your phone if its on your left arm and the phone is in a pocket on the right etc, or is the BT being easily blocked by the body

    Which will give best results for Looping – and which should be avoided or used ‘at risk’ – what are the reasons one wins over the other

    Availability on the NHS – when will we see them available in the CCGs to add to a repeat script (you can guess I’m British right?)

    Support on which apps for which sensor (currently running Patched Libre App, xDrip, Nightscout and AndroidAPS to get readings into the apps I want, which is a bit of a faff)

    Compatibility with which pumps (assuming no DIY looping is used)

    Ease of use to apply sensors – are they suitable for children as well as adults

    Expiry times and cost per day if self funding – are there any hacks to extend sensor life?

    Comfort and stickyness – I currently wear an L2 and need to keep it in place using Tagaderm film, other wise they peel off or get knocked off in 2 weeks

    Sensor security – can the data signal be ‘hacked’ or is it encrypted, can more than one reader access the info or do we need to start a new one if my phone dies?

    Manufacturer support – Are they response to errors/problems – will we need to wait for 2 weeks before getting a replacement delivered meaning we need to keep a stock of 2 sensors ‘just in case’

    How often do they fail on start-up, or during use (L2 seems a fair bit worse than L1)



    • I can answer a couple.of those questions for you straight up.

      1. None of those I’m testing here are compatible with any available commercial AID systems.

      2. Availability on repeat prescription is down to your local CCG (soon to be ICT) adding it to their formulary. All three should be on the tariff from August 1st, but that doesn’t guarantee local availability.

      Depends what you mean by hacked… So far, we already know that Libre2 and Dexcom One can be used in DIY systems, but as they only have one Bluetooth channel, as does the Glucomen Day, connecting simultaneously to an additional device is not possible. Both Aidex and Dexcom can be reconnected on a different phone if your current phone does. Libre2 can’t as far as I’m aware.

  4. Tim, I am never sure if you are mad, a genius, or an engaging mix of both…. are you wearing them all at once?

    • I’ll be wearing them all on the same arm to try and minimise differences in interstitial fluid…

  5. I have been using the Libre2 CGM for several years as it is/was the only one available free to me on NHS prescription. I have recently progressed from MDI to an insulin pump anticipating (and hoping)that the Libre3 will also become available on NHS prescription and, at the same time interact with my TSlim insulin pump. If this happens life will be a good deal easier, but even if it doesn’t I am happy to continue entering BG readings manually as well as relying on the built-in alarms, even though the alarm usually comes too late to rectify a low blood sugar. If, as advertised, the Libre3 can anticipate low BG’s in advance, this would be a significant advantage.

    • As far as I’m aware, there are a couple of hurdles to L3 getting FDA iCGM approval due to the issues it has with Vitamin C.

  6. AS far as i’m aware Abbott are not pushing for L3 to be on prescription. It will remain as competition to G6 and G7 when it launches and G6 is phased out. Dex 1 and L2 will be direct competitors and on prescription. L3 and G7/6 will not be on prescription (my understanding) but given the recent NICE guidance should be available – the reality is that the funding models for this are not yet in place, as the NICE guidance has not resulted in any additional funds to actually do any of this.

    • I think you’ve summed that up pretty well.

      I don’t expect to see separate funding for L3 or G6/G7, as I expect them to be rolled into the Closed Loop report, and then funding for that, however it ends up working!

  7. I’m keen to understand better the options for looping. It looks like the ONE could replace the self-funded G6 in my AAPS set-up, but I’d like to understand better the options and limitations. Any prospect of a BYODA-equivalent for the ONE, or are they just completely different animals? I’m finding it hard to get much info on the ONE, esp as its name means that searching on FB groups throws up lots of false positives, even using “Dexcom ONE”. Thanks, and I love you blog

  8. Again , as far as I know Dex 1 will not connect with pumps – not in its native form….

    Good comparison chart here –

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