Continuous glucose monitoring (CGM) and flash

You can check your sugar (glucose) levels at any time with a continuous glucose monitor (CGM) or flash monitor.

It lets you see patterns in your levels and check if your glucose is too high or low. It can help you control your blood glucose levels, as you'll have more information and can take action quickly.

It can help you and your diabetes team see:

If your blood glucose reading is:

How it works

A CGM or flash monitor is made up of:

With CGM, the sensor sends results to the receiver or your phone every few minutes. You can see your glucose levels on your receiver at any time. Some types can send results to an insulin pump, so you can see your glucose levels on your pump.

Some CGMs can work with an insulin pump to automatically deliver the amount of insulin you need into your body based on your glucose level readings. This is called a hybrid closed loop system or artificial pancreas.

Diabetes UK has more information about closed loop systems for type 1 diabetes

With flash, you need to scan the sensor with the reader or with your phone to see the results.

There are several different types of CGM. The only type of flash monitor available is the Abbott FreeStyle Libre 2. The original Abbott FreeStyle Libre has been discontinued.

Some types of CGM have optional alarms to alert you if your blood glucose levels go too low or too high. The Abbott FreeStyle Libre 2 also has an alarm.

You generally need to replace a sensor every 7 to 14 days, depending on the type of monitor you have.

Interstitial fluid glucose readings are a few minutes behind your blood glucose levels. This means you'll still need to do finger-prick checks every now and then, particularly when you drive or have a hypo.

To get the best out of CGM or flash, you'll need to look at the information it gives you with your team.

Getting CGM or flash on the NHS

CGM or flash glucose monitoring should be available on the NHS to anyone with type 1 diabetes.

Children and young people will usually be offered CGM. Adults will usually be offered a choice of CGM or flash.

Ask your diabetes team about getting CGM or flash glucose monitoring.

Learn more about CGM and flash from Diabetes UK

Page last reviewed: 6 July 2021
Next review due: 6 July 2024