CGMS models pros and cons

Continuous Glucose Monitors

Hey Patchers,

Seeing as NJaP wouldn’t be here without them, this post is dedicated to the wonderful, the magical, the incredible CGMs (continuous glucose monitors)! As I’m sure we all agree, CGMs are pretty darn life-changing. Whether you have T1D yourself, or know someone who does, let’s give a round of applause to these little devices that do a lot of the T1D hard work for us.

And whilst we’re in a congratulatory mood, let’s give it up for the NJaP family of patches! Always there to keep your CGM on point. The Oscars just revealed its winners, and we know who should have got the prize for the best supporting role. (hint: our NJaP patches).

CGM 101

Although there are different products on the market, all CGM systems broadly work in the same way. They do what they say on the tin – they continuously monitor glucose levels throughout the day.

NB. They don’t actually measure your blood sugar levels but instead measure the amount of sugar in the fluid under the skin, called interstitial fluid.

Why is this great?

Well, unlike finger prick testing, which gives you one solitary reading with no indication of which direction your blood sugar is going in, CGMs can help you and your diabetes team see:

  • If blood sugars are going up or down;
  • How your levels change over time;
  • What happens to your blood sugars overnight;
  • Patterns that occur after specific meals or during exercise;

How do they work?

  • A small sensor sits underneath the skin that reads how much sugar is in the interstitial fluid;
  • A transmitter, which is attached to your sensor, sends data wirelessly to a receiver;
  • The receiver displays your blood sugar levels. This can either be a handheld device, a compatible smart device like a phone or watch, or an insulin pump; 
  • A small sensor sits underneath the skin that reads how much sugar is in the interstitial fluid;
  • A transmitter, which is attached to your sensor, sends data wirelessly to a receiver;
  • The receiver displays your blood sugar levels. This can either be a handheld device, a compatible smart device like a phone or watch, or an insulin pump; 

CGM systems also come with software so you can analyze results, look for patterns and help to better plan treatment decisions in the future.

Without further ado, let’s introduce the CGM systems.


Dexcom’s latest product is the G6 (following on from the G4 & G5), which offers an easy and (mostly) pain-free insertion and a sensor that lasts up to 10 days. The company places emphasis on ‘continuous’, explaining that the data can tell a story for the wearer.

The Dexcom G6 can be used by anyone above 2 years old, no matter what insulin pump or pen you use. The sensor is worn on the tummy and you can shower with it, exercise with it, swim with it (or, as some of the NJaP team like to do – take hour-long baths with it on!).

The app has arrows that show the speed and direction your blood sugar is going in. A double down arrow, for example, shows that your blood sugar is falling quickly.

You can set high- and low-level ranges, so when your glucose reading is at or below a threshold, your Dexcom receiver can alert you. This means you can treat before a hyper or hypo hits.

The Dexcom G5 and G6 systems are the only ones licensed to make treatment decisions without confirmatory finger-prick tests. 

Pros: no need to calibrate the G6; proven to lower HbA1c.

Cons: Can be prohibitively expensive; adhesive on the sensor is poor (this is where our patches come in!)

Medtrum A6

This system uses a tiny, flexible, hair-like sensor that provides 720 sensor glucose readings per day. The data are recorded and fully uploaded automatically into a cloud-based system, meaning there is no risk of data loss.

The CGM system is integrated with their insulin pumps, providing a semi-closed loop insulin management system. This allows for the pump to suspend when the system detects low glucose readings.

Pros: CGM data can be integrated to the pump, providing a semi-closed loop system of diabetes management.

Cons: Anecdotal concerns that the accuracy is poor compared to other CGM systems.


Medtronic offers two CGM systems: The Guardian Connect is a standalone system, whereas the Enlite can be integrated with the MiniMed 640G insulin pump systems.

For the Enlite system, Medtronic have developed exclusive SmartGuard technology that protects against hypos. Insulin is automatically stopped when glucose is predicted to approach a pre-set low limit and then insulin resumes when levels recover. Wearers can set multiple low limits for different times of the day.

This is the only CGM system that can alert you of potential highs and lows up to 60 minutes in advance.

Pros: the Enlite sensor is now 80% smaller in size compared to a former version.

Cons: Sensors only last up to 6 days.

Accu-Check Eversense XL

Like other CGMs, a smart sensor reads glucose in the interstitial fluid, then a smart transmitter is worn on the arm, wirelessly powering data to a receiver.

The main difference with the Eversense XL is that a new sensor is fully inserted under the skin for up to several months at a time. As such, the Eversense XL is the first implantable CGM.

Now we get onto some technical stuff, as explained by the company themselves:

“Glucose reversibly binds to the sensor’s polymer coating and the amount of light emitted by the polymer coatings rises and falls with changing glucose levels. Photodetectors in the sensor measure the emitted light and wirelessly send these measurements to the transmitter, which calculates glucose concentration, rate of change and direction.

This glucose data is sent wirelessly to the smartphone app that provides real-time tracking, intuitive displays to help identify patterns, and information to help stay in range. The smart transmitter also provides on-body vibration alerts even if your phone is not nearby or is switched off.”

Pros: The sensor can last up to 180 days.

Cons: The implant requires a medical professional.

Freestyle Libre

The Freestyle Libre, also known as a flash glucose monitoring system, is not technically a CGM, but operates in a similar fashion.

A flash system is made up of:

  • a sensor you stick to your arm (about the size of a £2 coin)
  • a reader (a small device you use to scan the sensor to see your sugar levels. You can also use a smartphone app to scan the sensor.)

Sensors usually last for 14 days and they are waterproof in up to 1meter for 30 minutes.

Unlike a CGM system, flash does not have an alarm for hypo or hyper warnings.

With a CGM, your sugar levels are always visible on the screen of your receiver. With flash, you use the reader to scan the sensor when you want to see your levels.

Check our Freestyle Libre patches.

Pros: more affordable than a CGM

Cons: no hypo or hyper warning alarms

The Freestyle Libre 2

The new version of the Libre system, rolled out in 2018 in Germany and across Europe, can alert users in real-time of hypos and hypers. The new system uses Bluetooth technology and blood sugar alarms, making it more competitive with Dexcom and other ‘true’ CGM companies, but it is not more expensive than the original Freestyle Libre.

Pros: despite better functionality, it remains at the cheapest price-point.

Cons: not widely available across the world.

MiaoMiao 1 & 2

MiaoMiao is a smart reader. It sits on top of the Libre sensor and turns it into a CGM (hurrah!) sending your blood sugars to your phone or watch every 5 minutes. 

Users will need compatible apps and sensors to use the MiaoMioa 1 and MiaoMiao 2 systems. Currently most of the popular CGM applications, like xDrip+, Tomato, Glimp and Spike all work fine. However, different applications work for different sensors.

MiaoMiao 2 is slimmer and lighter and has better connectivity than MiaoMiao 1. It’s also easier to attach with FreeStyle Libre sensors.

Check our MiaoMiao patches.

Pros: You just need to buy 1 MiaoMiao – it can last for years.

Cons: Anecdotal reports of people having skin reactions to the adhesive.

So there we have it – our round-up of the current CGMs on the market!

And whilst all these CGMs are the real star of the show, a big hand needs to go to our NJaP patches – these little pops of color that ensure your CGM can do the best job possible. We like to think of our patches as the quiet achievers. Dependable, reliable and always there to get your back. Have you seen our latest range?

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