What Is a CGM?
What Is a CGM & How Does It Work? Track Blood Sugar on Your Phone in Real Time
By GlucoRx Editorial Team · Last updated 14 September 2026
A continuous glucose monitor (CGM) is a small, body-worn sensor that tracks your glucose around the clock and sends the readings to your phone. A hair-thin filament sits a few millimetres under your skin and measures glucose in the fluid around your cells — the interstitial fluid — not in your blood, so a CGM is minimally invasive, not non-invasive. The GlucoRx Vixxa 2, for example, is worn on the back of the upper arm, takes a reading every 60 seconds (about 1,440 a day) and streams them to the Vixxa CGM app over Bluetooth.
Because it reads interstitial fluid rather than blood, a CGM value can lag your actual blood glucose by roughly 5–15 minutes, and the gap is largest when your glucose is changing quickly. That is why a confirmatory finger-prick is still advised when a reading does not match how you feel or before you treat a suspected low. A CGM is a monitoring aid, not a treatment; individual results vary and it is not a substitute for medical advice.
What is a CGM?
A continuous glucose monitor is a wearable sensor that measures your glucose continuously, day and night, instead of at single moments like a finger-prick test. A hair-thin filament sits a few millimetres beneath the skin, and the small sensor worn on top sends each reading wirelessly to an app on your phone.
Crucially, a CGM does not measure the glucose in your blood directly. It measures glucose in interstitial fluid — the fluid that surrounds the cells just beneath your skin. Because the filament pierces the skin to sit in that fluid, a CGM is minimally invasive; it is not a “non-invasive” or needle-free device. The sensor does the measuring, and your phone or watch simply displays the readings.
How does a CGM measure glucose?
Most modern CGMs, including the Vixxa 2, use an electrochemical sensor. The thin filament sitting in the interstitial fluid is coated with the enzyme glucose oxidase; as glucose reacts with the enzyme it generates a tiny electrical current, and the size of that current reflects how much glucose is present. The sensor converts this signal into a glucose value at regular intervals.
Because glucose has to move from your bloodstream into the interstitial fluid before the sensor detects it, CGM readings can trail your actual blood glucose by roughly 5–15 minutes (sometimes up to about 20). This lag is largest when your glucose is moving fast — after a meal, during or after exercise, or during a low — and smallest when your glucose is stable. It is why a CGM reading and a finger-prick can differ at those moments without either being wrong.
How do I see the readings?
The sensor streams your readings to a companion smartphone app. With the Vixxa 2 this is the Vixxa CGM app, which runs on iOS 15 and later and Android 10 and later and connects over Bluetooth — there is no phone-tapping or NFC scanning needed to get a reading. In the app you can see your current glucose, a trend arrow showing which way it is heading, and your history.
You can also set customisable high and low alerts that notify you when your glucose crosses a level you choose. The Vixxa 2 offers these threshold high and low alerts. Some other CGM systems add further features — such as predictive alerts that warn of a low before it happens, or the ability to share your readings with a family member or carer (for example Dexcom Follow or Abbott LibreLinkUp) — which the Vixxa 2 does not offer.
How does the GlucoRx Vixxa 2 work?
The Vixxa 2 is a real-time CGM that measures interstitial-fluid glucose and streams it to your phone. Its key specifications:
- Worn on the back of the upper arm.
- Takes a reading every 60 seconds — about 1,440 readings a day.
- About a 60-minute warm-up after you apply a new sensor, before it starts showing readings.
- Worn for up to 15 days per sensor.
- Connects to the Vixxa CGM app over Bluetooth (iOS 15+ / Android 10+); no NFC scanning.
- Customisable threshold high and low glucose alerts.
- A compact sensor: about 22 mm across, 4 mm thick and 2.16 g.
- Rated IP68 for water resistance (tested to 2 m for up to 60 minutes).
- Intended for adults aged 18 and older.
Do I still need finger-pricks with a CGM?
A CGM greatly reduces routine finger-pricking. With approved integrated CGMs you generally do not need to finger-prick to calibrate or for everyday treatment decisions, as long as your symptoms match the reading, and the Vixxa 2's CDSCO-licensed intended use describes it as designed to replace fingerstick testing for treatment decisions.
Even so, device guidance advises keeping a blood glucose meter for confirmatory checks: do a finger-prick when a reading does not match how you feel, when your glucose is changing rapidly, or before you treat a suspected low. Dexcom's safety guidance, for example, tells users to confirm with a finger-prick before a treatment decision if their readings do not match their symptoms or expectations.
For a fuller comparison of the two methods — accuracy, convenience and cost — see our guide on CGM versus finger-prick testing. A CGM is a monitoring aid, not a treatment; individual results vary and it is not a substitute for medical advice.
Frequently Asked Questions
Is a CGM the same as a non-invasive or needle-free glucose monitor?
No. A CGM has a hair-thin filament that sits a few millimetres under the skin, so it is minimally invasive rather than non-invasive or needle-free. It measures glucose in interstitial fluid — the fluid around your cells — not in your blood, and sends the readings to your phone.
Where do you wear the Vixxa 2, and how often does it read?
The Vixxa 2 is worn on the back of the upper arm. It takes a reading every 60 seconds — about 1,440 a day — and can be worn for up to 15 days per sensor, after roughly a 60-minute warm-up when you first apply it.
How do CGM readings reach my phone?
The sensor connects to a companion app over Bluetooth — the Vixxa CGM app on iOS 15+ or Android 10+ — with no NFC scanning needed. The app shows your current glucose, a trend arrow and your history, and you can set customisable high and low alerts.
Why does my CGM reading differ from a finger-prick, and do I still need one?
A CGM measures interstitial fluid, which can lag blood glucose by about 5–15 minutes, so the two can differ when your glucose is changing quickly. A confirmatory finger-prick is still advised when a reading does not match your symptoms or before treating a suspected low. A CGM is a monitoring aid, not a treatment; individual results vary and it is not a substitute for medical advice.
Important information & sources
AI-assisted content. This page was created with the help of AI and public sources, and reviewed against them, as of 14 September 2026. Details may change — please verify current specifications and prices with the manufacturer or an authorised seller before you rely on them.
This page is published by GlucoRx, the manufacturer of the Vixxa 2 sensor. It is for general information only and is not medical advice. Individual results vary. Consult your doctor or diabetes care specialist before making changes to your monitoring or treatment.
Specifications and prices were retrieved in September 2026 from the sources below and may change — please verify current details with the manufacturer or an authorised seller before relying on them. The interstitial-fluid lag is a typical range that varies by device and by how quickly your glucose is changing.
All trademarks are the property of their respective owners. Dexcom and Dexcom Follow are trademarks of Dexcom, Inc.; FreeStyle Libre and LibreLinkUp are trademarks of Abbott. If you spot an error on this page, please email info@glucorx.co.in and we will correct it promptly.
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