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Home > Knowledge & support > Managing type 1 diabetes > Guide to type 1 diabetes technology > Continuous glucose monitoring
A continuous glucose monitor, or CGM, is a small wearable device that measures your glucose levels in real-time. It uses a sensor to continuously send information to a handset or compatible mobile phone so that you can see what your current levels are and whether they’re heading up or down. You can also set alarms to signal if your glucose levels are going too high or too low and see your glucose trends over time.
You attach a CGM directly onto the skin, usually on the upper arm or stomach. A short wire from a sensor goes under the skin and senses how much glucose there is in the fluid between your blood vessels and cells (this is called interstitial fluid).
A transmitter then beams this information to a receiver, which might be a handset, your compatible mobile phone or compatible insulin pump.
You wear the sensor for six to 14 days (depending on the make of the CGM) and then replace it with a new one.
CGMs can be used however you take your insulin, whether you are using multiple daily injections (MDI) or an insulin pump.
One of the main benefits of CGM is that it allows you to get a wider picture of your glucose levels. When you use a blood glucose meter, you only see what your glucose levels are at the time that you take the measurement. With CGM, you can see your current level, where it’s heading, and review the data over the last few hours or days. This means that you get a fuller picture of what is happening to your levels throughout the day and night, for example, when you’re exercising, eating or sleeping.
A CGM alerts you if your glucose levels are heading low or high. This allows you to take action so you can minimise or avoid hypos or hypers before they happen. CGMs can help improve your time in range, which is very important when you’re managing type 1 diabetes.
CGM allows you to easily share your glucose data with your loved ones, carers or healthcare team, in real-time or for long-term review. If you’re a parent or guardian of a child with type 1, this means you can see their glucose levels remotely or alert the school if your child is having a hypo. Sharing it with your diabetes team means they can look at the data and see your glucose trends over time, as well as looking at your Hba1c.
“We both wear the Dexcom G6 continuous glucose monitoring device to help manage our blood sugars. It has been a life changing piece of technology that has improved both our time in range as well as providing constant reassurance” – Diabetic Duo, Beth McDaniel and Ellen Watson.
“I use the Freestyle Libra 2 and injections, and before using the technology, it was quite stressful trying to manage my blood glucose levels with the finger prick testing. So for me it’s been a bit of a game changer.”
Using a CGM can take time to get used to, but the downsides are minimal.
Because a CGM doesn’t measure the amount of glucose in the blood itself, you may also need to do a finger prick measurement to calibrate the system or confirm the reading is accurate before acting on it, for example treating a hyper. This can depend on the type of CGM you’re using, so always check with the manufacturer or your Diabetes Healthcare Team.
Some people experience something called alarm fatigue, when you feel annoyed or overwhelmed by the number of alerts from your CGM. Your Diabetes Healthcare Team can help you set the best levels for your alerts, so you don’t keep being alerted about something if you’re not planning to take any action. For example, you may decide not to correct high glucose levels until it reaches a particular number.
Flash glucose monitoring is when you use the Freestyle Libre 2 sensor with the dedicated handset. When you want to get a reading you scan – or ‘flash’ – the sensor. When you use the Freestyle Libre sensor with the app on your phone, it gives continuous real-time readings, which makes it a CGM.
A CGM can work with an insulin pump to form a hybrid closed loop system (also known as an artificial pancreas or automated insulin delivery). Using this helps to automate your type 1 treatment and reduce the number of decisions you need to make every day.
Our hybrid closed loop page has information about which CGMs, insulin pumps and programmes work together to make a hybrid closed loop system.
The manufacturers sites listed above will also tell you what technology each CGM is compatible with.
A CGM can work with a smart insulin pen, which is a type of insulin pen that records how much insulin you take and when. Connecting a smart pen with a CGM can help you record information on your glucose levels and the amount of insulin you’re taking, which can help you make decisions about your treatment.
These are the main manufacturers of CGMs. Visit their websites for more information:
GlucoRX and Medtrum are also available but there is currently limited evidence of accuracy for people with type 1.
CGMs, as well as flash sensors, are usually white or a light grey. This can make them stand out, particularly if you have dark skin, and make some people feel self-conscious. Adhesive patches are available in a variety of skin tones, colours and patterns and you can search for them online.
The NHS recommends CGM for everyone with type 1 diabetes in England and Wales. CGMs that work with insulin pumps to form a hybrid closed loop system are normally approved by your hospital-based Diabetes Healthcare Team. Alternatively, your GP can prescribe CGM, but most of the CGMs available on prescription don’t work as part of a hybrid closed loop system. Find out more about which CGMs work with which insulin pumps in hybrid closed loop systems.
Get more information on how you can access CGM on the NHS in England and Wales, Scotland and Northern Ireland.
Most CGM sensors cost around £40 – £60 each. Unless you have a compatible mobile phone, there is also an initial cost for a handset/receiver. There are then ongoing running costs for sensors, transmitters, and adhesive covers. However, in England and Wales you should be able to get the CGM system you need on the NHS.
“Now I have the Dexcom G6 and the Omnipod and I love both of them, they’re amazing… The Dexcom can send my parents my blood readings at all times, and they can text me and tell me like you need to sort this out, if I’m not aware of it. It’s so much easier for doing sports and all.”
Find out what’s available to you on the NHS and how to access it.
Learn more about hybrid closed loop technology (also known as the artificial pancreas) and how it can help you manage your type 1
Yachtsman Jack trigger on the tech that helps him on the waves
A smart insulin pen is a reusable self-injection pen, which records information about how much insulin you inject and the timing of it.
Blood glucose meters measure the amount of glucose in the blood. They are an important part of managing your blood glucose levels.
Continuous glucose monitoring can help you manage your glucose levels in real-time and relieve the burden of having to do multiple finger prick tests throughout the day.
A flash glucose monitor is a small wearable device that you scan with a reader or mobile phone to check your glucose levels.
Hybrid closed loop technology – also known as the artificial pancreas – automates many of the decisions that you have to make on a daily basis when you have type 1 diabetes.
Open source and DIY systems are sometimes used by people with type 1 diabetes or people caring for someone with type 1 to help manage the condition.
Apps can help you manage type 1 diabetes, from logging your insulin doses, glucose levels and the food you eat, to helping you count carbs and order prescriptions.
