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NEW TO NHS: What is the Dexcom ONE CGM system?

  • 7 min read

Man showing glucose level on phone and wearing Dexcom CGM on arm.


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Updated 9 October 2022


- No scanning

- Updates every 5 minutes

- IP68 waterproof rating (24 hours up to 2.4m)

- cost to NHS is same as FreeStyle Libre

- no app for carers to follow

Dexcom ONE CGM vs Libre 2

Dexcom ONE is now available on NHS prescription and in this blog we review the features of this real-time CGM. 


Who is the Dexcom ONE for?

Images of Dexcom ONE CGM.

The Dexcom ONE is a less expensive option for those wanting a real-time CGM but not needing all the options available on the G6 or G7. In essence it is a pared-down G6 with some reduced functionality.


About the Sensor

The sensor is the same shape as the G6, an irregular lozenge shape and is worn on the back of the upper arm or abdomen (those aged 2-17 years can also place the sensor on the buttocks).

This CGM has two separate parts, a sensor that lasts for up to 10 days and a transmitter that can be recharged and lasts up to 90 days.

As Dexcom G6, the Dexcom ONE is approved for those aged 2 years and older.


Application process

 Dexcom ONE CGM system applicator being attached on abdomen.

The sensor is applied with a one-piece applicator in the same way as a G6 sensor. The underlay is attached simultaneously and once attached the user needs to ‘snap’ in a separate transmitter. Sensors and transmitters need to be paired to the app. This is done by either scanning a QR code or keying in the serial numbers from these components into the app.

There is a two-hour warm-up period before glucose levels appear directly on a phone or watch and users keep their phone (as the receiving device) within 6 metres of the transmitter during this time.


Swimming, Sports & Exercise 

Dexcom ONE is water-resistant once the transmitter is snapped in place and can be worn for swimming, showering and bathing. As with the G6, the rating (IP68) of the product is that it can be worn for up to 24 hours in water to a depth of 2.4 metres. This is an advantage over the FreeStyle Libre system which is rated to IP67 standard and limited to use in water for up to 30 minutes to a depth of 1 metre.

Remember, that no product is truly waterproof and covering it is unlikely to mean that it’s more water-resistant or waterproof.

Users won’t get readings if the receiving device/phone is more than 6 metres away.

Read also: Swimming with a Libre or other CGM


Integration with phone/smartwatch

Dexcom displaying glucose level on Apple Watch.

The Dexcom ONE App can be downloaded from the App Store (iOS) or Google Play (Android). There is a list of compatible phones on Dexcom’s website. Although it should be noted that at the time of publication this is not updated for the UK market and in current markets it is only certain Android Samsung phones and iPhones from 6S to iPhone 12 that are compatible.

Bluetooth is required for pairing the transmitter and sensor with the app, without this it won’t be possible to receive CGM data.

Glucose levels are updated every 5 minutes.


Reports & accuracy

The MARD* for Dexcom ONE is stated as 9.8% for adults and 7.7% for children. This is the same as Dexcom G6.

MARD is mean absolute relative difference and is used as a measure of CGM accuracy. The lower the percentage the more accurate the device has shown to be in trials.


Training and support

Dexcom have really developed their website from a user’s perspective, making it very easy to navigate and find support documentation and links to training resources including videos. There is lots of information and answers to many frequently asked questions, although personally I found this frustrating as it didn’t offer me any way to search myself. However, it is possible to submit a tech support ticket to answer a query not covered online.

The Training Resources includes a very helpful Checklist that covers everything you should need to get started with the CGM.



The lack of a recycling programme and the use of plastic are a bug bear of a significant number of users of Dexcom products.

The applicator is a one-time component and as it contains a needle for insertion it must be disposed of as biohazardous waste. Transmitters are reusable for a short period, up to 3 months, before disposal. Sensors are a one-time use and again need to be disposed of as biohazardous waste.


Costs & how to buy

Price information is not yet available for the UK market, however, the prices in Estonia indicate it will be significantly less than the current G6 prices, currently £51.25 for a single sensor with transmitters costing £200.

For Estonia: A starter kit including 1 x 10 day sensor and a transmitter is currently 59,90 euros (£50.60 approx). There are several options for subscriptions such as a monthly plan costing 118,90 euros (100.40 approx).

This appears to be aimed at being more competitive with the Freestyle Libre 1 and 2 which is currently available directly from Abbott at £48.29 excluding vat (sensor only).

Dexcom ONE will be available to purchase in the UK on the website from May 2022. There are different subscription models for self-funding the CGM.


How does it compare?

Dexcom produced a comparison of their range of CGM, G6, G7 and Dexcom ONE which highlights some of the key differences. Click here to see this table.

The key points to note about the Dexcom ONE are:

  • It is a pared-down G6 CGM;
  • It uses a different app and there are limited compatible phones;
  • It cannot be calibrated;
  • It does not offer the ability for carers to follow users;
  • There is no predicted low alert but low and high alerts are customisable;
  • The cost is expected to be significantly less than the G6, making it competitive with the FreeStyle Libre 1 and 2, but the ONE is real-time CGM and does not require scanning.
Read also: Libre 3 Update, Answers to your Q&As

    Future outlook

    The Dexcom ONE will be listed on the NHS for prescription from May 2022. This will expand the choices available on prescription so that users can choose a flash device ie. FreeStyle Libre 1 or 2, or real-time CGM selecting the Glucose Aidex or Dexcom ONE.

    You can find out more about the GlucoRx Aidex here.


    Features overview

    Size and shape

    Irregular lozenge shape



    Duration of wear

    10 days



    Frequency of updates

    Every 5 minutes



    Accuracy i.e. MARD

    9.8% Adults and 7.7% Paediatric – the same as Dexcom G6



    Approved ages

    From 2 years and older



    Approved insertion sites

    Abdomen and back of upper arms for adults and additionally on the upper buttocks for children.



    Components/insertion method

    One-piece single applicator for attaching sensor. After attachment, user attaches transmitter. Transmitters are reusable for 90 days.




    2 hours warm-up – the same as Dexcom G6








    IP68 rating, water-resistant for up to 24 hours up to 2.4metres depth



    Smartphone integration

    Limited compatibility to certain Samsung android phones and some iPhones. Important to check Dexcom’s website for list of compatible devices.



    Watch integration

    Expected to be smartwatch compatible, although this is not yet available.




    The app is different to the app for the Dexcom G6 and can be downloaded from the App store or Google Play. There are less options for users of the Dexcom ONE on the app.



    Data sharing

    No follower app. Data is available to healthcare professionals via Clarity reports.



    Transmission distance

    6 metres unobstructed



    Customisable alarms

    Yes, for high and low glucose.




    Optional alerts for high and low glucose but no predictive low alert which is an option on Dexcom G6.

    Dexcom ONE has a snooze alarm option for delaying a 2ndalert. Bluetooth must be enabled with sounds turned on to receive alerts.



    Separate reader/receiver




    Purchase options

    Price information is not yet available for the UK market, however, based on prices in Estonia it will be significantly cheaper than the G6 CGM and is expected to be competitive in terms of pricing with the FreeStyle Libre 1 and 2.




    Dexcom advise users to avoid using sunscreen and Insect repellent as these products can make the plastic of the sensor and transmitter crack.



    Thank you for reading. Please do submit comments below if you have any useful feedback on the use of this product. 



    Details and data is correct to the best of the author’s knowledge at the time this blog is published. We do not accept responsibility for any errors or omissions. Information is for guidance only and it is recommended that you confirm specific details and suitability yourself with the supplier, or your healthcare provider.

    Love My Libre is not associated or affiliated with any of the aforementioned medtech providers. Content here and on our website does not constitute medical advice or replace the relationship between you and healthcare professionals nor the advice you receive from them.

    The author of this blog has type 1 diabetes and uses the FreeStyle Libre 2 which is provided on NHS prescription. We do not have any affiliate relationship with Abbott or FreeStyle Libre.

    All third party devices and apps mentioned are registered trademarks of their respective owners. Images sourced from Dexcom Inc.


    1 Response

    Dan S

    Dan S

    June 09, 2023

    June 2023, I’m 47 and I’ve been using the Dexcom One for a few months now. It’s pretty good but currently still no smart watch functionality which is a real shame. Work arounds for the G6 utilise the share function which the One does not have. A plus is that while I’m at work I’ve been able to switch my Samsung S22 to ‘Do Not Disturb Mode’, in that mode I’m still able to override this for the Dexcom app. No ringtone or notifications from messages or email but the app can still notify me when required. Working in an office where phones are supposed to be shut away it would be really useful to connect to my smartwatch. I hate the thought of me checking my phone annoying colleagues that aren’t allowed.

    No follow function makes me think it’s a lot less suitable for children. I have a 4-year-old (not diagnosed but at higher risk) I certainly wouldn’t suggest it for that reason alone. Why turn off such a usefully function as the data is already in the app. Personally, I think Dexcom got this aspect completely wrong.

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