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Flash monitoring (FreeStyle Libre)

A flash glucose monitoring system measures your sugar (glucose) levels all the time throughout the day.

It can help you and your diabetes team see:

  • if your sugar levels are going up or down
  • how your sugar levels change over time
  • the past 8 hours so you can see what happens to your levels when you sleep at night

Flash does not actually measure your blood sugar levels. It measures the amount of sugar in the fluid under your skin, called interstitial fluid.

Interstitial fluid sugar readings are a few minutes behind your blood sugar levels. This means you'll still need to do finger-prick checks every now and then.

The measurements can help you and your diabetes team make decisions about your treatment and any adjustments you need to make.

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.

You still need to do some finger-prick tests, particularly when you drive or have a hypo.

Like a continuous glucose monitoring (CGM) system, FreeStyle Libre 2 has optional alarms for hypo or hyper warning.

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.

How to get a flash system

The only flash system available is the Abbott FreeStyle Libre.

Getting a flash system on the NHS

The FreeStyle Libre is available on the NHS.

You must meet certain criteria to get it on prescription, such as:

  • having to test your blood glucose more than 8 times a day
  • having disabling hypos
  • being pregnant and having type 1 diabetes

Find out more about the criteria for getting flash glucose monitoring on Diabetes UK.

You can read more about glucose monitoring for patients living with diabetes on the NHS England website.

You can buy a flash system yourself

As a rough guide, it costs around:

  • £133.29 for a starter pack of a reader and 2 sensors (excluding VAT)
  • £48.29 for a sensor (excluding VAT)
  • £48.29 for a reader (excluding VAT)

Speak to your diabetes team if you're thinking of buying a FreeStyle Libre.

Page last reviewed: 1 September 2021
Next review due: 1 September 2024