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Flash glucose monitoring

A flash glucose monitor is a small wearable device that you scan with a reader to check your glucose levels.
Content last reviewed and updated: 05.02.2024

A man using flash glucose monitoring - holding a mobile app and glucose sensor on his arm

What is a flash glucose monitor?

A flash glucose monitor reduces the number of finger prick glucose tests you need to do. Flash can be a good way to measure your levels more easily and frequently than with blood glucose meters alone.

A flash glucose monitor is often known by its brand name, Freestyle Libre 2. This is the only kind of flash glucose monitoring available, as the technology has been largely overtaken by continuous glucose monitoring (CGM). In fact, the FreeStyle Libre 2 sensor works as a CGM when used with a smart-phone. It only works as flash if it is used with the dedicated reader.

How does flash glucose monitoring work?

You attach a sensor, which is about the size of a £2 coin, to the upper arm and keep this on for up to 14 days. A filament from the sensor sits under the skin to measure how much glucose there is in the fluid between blood vessels and cells (this is called interstitial fluid).

This filament is put in place with a needle which is then retracted back into the inserter. It all happens in an instant – all you need to do is press a button.

When you want to check your glucose levels, you scan or ‘flash’ your sensor with the handset that comes with the sensor to get a reading.

The reading gives you:

  • your current glucose level
  • a graph of your glucose level over the last eight hours
  • a trend arrow to show if your blood glucose is rising, stable or falling

It’s recommended that you check any rapidly changing glucose readings or any readings which don’t match your symptoms with a finger prick measurement.

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What is the difference between a flash glucose monitor and a continuous glucose monitor?

The Freestyle Libre 2 sensor works as flash when you use it with the handset that comes with it. This means that it only gives you a reading when you scan it with the handset.

If you use the Freestyle Libre 2 sensor with the Libre Link app on your smartphone, it works instead as a continuous glucose monitor (CGM) and transmits data to your phone or handset all the time.

Do flash glucose monitors work with other tech?

No, flash glucose monitors aren’t compatible with other tech, like insulin pumps. If you want to integrate your glucose measurement with your insulin intake, visit our guides on CGM, smart pens or hybrid closed loop technology.

What sensors are available?

The only flash sensor that is available is the FreeStyle Libre 2. The FreeStyle Libre 3 is a CGM, not flash.

How much does a flash glucose monitor cost?

Flash sensors cost around £50 each and last for up to 14 days.

Can I get a flash glucose monitor on the NHS?

Flash should be available on the NHS to anyone with type 1, but it can still depend on where you live. Find out whether you can access flash on the NHS in England and Wales, Scotland and Northern Ireland.

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