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Flash glucose monitoring

Flash glucose monitors are a way of measuring your sugar levels without having to prick your fingers. There is only one flash glucose monitor manufactured at the moment. This is called the Freestyle Libre.

Here we’ll explain how to get a flash glucose monitor and how they work. We’ll take you through the pros and cons too, to help you make a decision about whether this tech is right for you – it’s not for everyone.

Go to our information on troubleshooting for Freestyle Libre2 users

What is flash glucose monitoring?

A flash glucose monitor is a small sensor that you wear just under your skin. We call it Flash for short. 

It records your glucose (sugar) levels continuously throughout the day and night. You can find out your levels by scanning the sensor whenever you want to.

The sensor doesn’t actually measure your blood sugar level, it measures the amount of glucose in the fluid that surrounds your body cells – called interstitial fluid. There is a small time delay when checking this fluid, especially after eating or if you're exercising. So your flash glucose monitor result isn't always exactly the same as your finger-prick result. 

“Flash is the most important tool I have (next to insulin of course). … I use my Libre every single day, and it has vastly improved the quality of my life.” 

Erin, Flash user

This means you'll still need to do a finger-prick check if you’re thinking of changing your treatment at any point, like if you need to take more insulin or if you're treating a hypo, so you can get the most accurate result.


How can I get a flash glucose monitor?

From April 2019, Flash became available on prescription across England to those who meet the criteria. This was made possible by our tireless campaigners in our Fight for Flash

Unfortunately, this doesn’t mean everyone who could benefit from Flash will be able to access it. There are clear criteria that you need to meet in order to get tech on prescription from the NHS. 

Here’s the criteria you need to meet in order to get Flash for free on prescription, depending on where you live. We understand that it can be really frustrating if you face issues getting your tech. That’s why we’ve put together advice to help you challenge the decision if you don’t meet the criteria. You can also give our helpline a call for more information and support. 


You need to meet one or more of these:

  • You have type 1 diabetes and you need to check your blood sugar level more than eight times a day.
  • You have type 1 and have previously paid for Flash and can show it has improved your HbA1c. 
  • You have type 1 and have severe hypos or have reduced hypo awareness.
  • You have type 1 and are unable to test regularly due to a disability.
  • You’re a pregnant woman with type 1 diabetes.
  • You have type 1 or type 2 diabetes and use insulin and are identified as having a learning disability. You'll need to be on your GP's learning disability register. You and your supporter can check with your GP if you're on their register and ask to be added if you're not. Find out more about the disability register and see our easy-read health information for people with learning disabilities and their supporters.
  • You have cystic fibrosis-related diabetes and you take insulin.
  • You have another type of diabetes that you treat with insulin and you’re also on haemodialysis, which is a procedure that takes over kidney function when your kidneys aren’t working. You’ll also need to show that you have to check your blood sugars more than eight times a day to keep your blood sugar levels in your target range.
  • You work somewhere that your diabetes team have said isn’t appropriate for finger-pricking. (From October 2020 you should be offered continuous glucose monitors (CGM) as the technology of choice) Or there are emotional or social factors that mean you can’t prick your finger. Both of these cases mean you can have a six-month trial of Flash.

If you meet any of these criteria, you must also:

  • learn how to use Flash with a healthcare professional or carer, where appropriate 
  • agree to check your levels eight or more times a day and use the sensor 70% of the time when you check
  • agree to regular reviews with your local diabetes team.

Go to NHS England to find out more about the criteria and if you meet them.


To qualify for Flash in Wales you must meet one of the following criteria:

  • You check your blood sugar eight or more times a day. 
  • You have a consistently high HbA1c despite checking 10 or more times a day and you can show that Flash will help you reduce that.
  • You have regular hypos (more than two a week) or you have lost hypo awareness.
  • You have had more than one severe hypo a year with no obvious cause.
  • You have an extreme fear of hypos. 

You can find the full criteria on the NHS Wales website.  

Northern Ireland

In Northern Ireland, there’s no strict criteria but there are a list of things your diabetes team must take into account:

  • You check your blood sugar more than four times a day, can show that you know how to count your carbs and manage your insulin doses.
  • You have four or more hypos a week or two severe hypos in a year.
  • You have reduced hypo awareness.
  • If you find it difficult to keep your HbA1c levels down and it’s reasonable to believe Flash would help you.
  • You have severe physical, emotional or work-related issues that affect your ability to manage your blood sugar levels.
  • You are currently using Flash and there is good evidence that it’s helping you manage your diabetes.


In Scotland, there’s a mixture of criteria. Here you’ll find a list of the Health Boards (PDF, 342KB) and their published criteria.

“This little piece of tech has significantly changed how I manage my diabetes.” 

Adrian, flash user

How does a flash glucose monitor work?

A flash glucose monitor has two parts:

  • A sensor that you wear just under your skin which measures your sugar levels.
  • A reader that you or someone else can swipe over the sensor to get both your sugar level and the trend of your levels. You can also scan the sensor with your phone.

Each time you scan your sensor, you can access the last eight hours of sugar levels. Flash glucose monitoring also comes with software so you can analyse your results and see patterns in your sugar levels. 

You generally wear a sensor for about 14 days, after that you need to put on a new one.

Sensors should be worn on the arms only, and we recommend that they aren't placed over areas with tattoos as this could impact your results.

What’s the difference between flash glucose monitoring and continuous glucose monitoring?

Continuous glucose monitors (CGM) measure your sugar levels continuously and send data to your display device (a handheld monitor or pump). So you can set alerts for high, low or rate of change. With flash glucose monitoring, you only get your reading and trends when you scan your sensor.  

If you want to find out more about CGM, we have loads of information.

Pros and cons of using a flash glucose monitor

Diabetes technology is a wonderful thing, but it certainly isn’t for everyone. 

Some people feel uneasy about getting lots of data, and for some people it gives them more confidence. We’ve got more information to help you work through these different feelings about using diabetes tech. And you can always call our helpline to ask questions or just to talk it through.

Advantages of Flash

Disadvantages of Flash

You don’t need to do so many finger-prick checks.

You can’t set an alarm for high or low sugar levels, so it won’t help you recognise a hypo.

You can see trends, like when your sugar levels are starting to rise or drop, so you can take action earlier.

You can get overloaded with data, which can confuse or worry some people.

It can give you more confidence in managing your diabetes as you have more data to base decisions on.

You still need to do some finger-prick checks.

You can get your sugar levels in your target range more often as you have more information about when you’re high and low.

You may find wearing the sensor irritating or you might not like the look of it.

You can see what your levels are like at times when you don’t normally test, like during the night (either by looking back at your own data or scanning someone else’s sensor while they’re asleep).


Your glucose levels can be shared with your diabetes team, so they can review and adjust your diabetes management. It also means that the information can be shared easily during virtual appointments.  

Driving and checking your blood sugars

You can use a flash glucose monitor to check your sugar levels when driving, but you must confirm your levels with a finger-prick test if:

  • your blood sugar level is 4 mmol/l or below
  • you have symptoms of a hypo
  • your monitor gives a reading that’s not consistent with the symptoms you’re getting – for example, if you feel like you’re having a hypo but the reading doesn’t show this.

Together, our campaigning changed the law on driving and checking your sugar levels. We’ve campaigned for years to make sure the law is fair. So that you can carry on driving and take the right steps to stay safe at the wheel.

Get involved with our campaigning today to make change happen.

Troubleshooting information for Freestyle Libre2 users

We know that lots of people have been reporting issues they've been having with the Freestyle Libre 2.

We previously collated some of these issues and fed this back to Abbott who have provided us with some 'Top Tips' for issues with Libre 2 alarms.

If you have any concerns or specific issues with your Freestyle Libre2, please contact Abbott directly via their Libre2 support pages. Or use the Abbott guides we're sharing below.

Top Tips for Freestyle Libre2 Android (1MB)

Top Tips for Freestyle Libre2 iOS (1MB)


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