What’s the difference between flash glucose sensing and continuous glucose monitoring?
Flash glucose sensing (FGS) is similar to continuous glucose monitoring (CGM) in that they both use a sensor and display trends. Unlike CGM, Flash or Libre does not transmit so it will not alert you to low or high glucose levels until you ‘flash’ the sensor. There are unregulated devices available which will take readings from the sensor every 5 minutes and transmit them to your smart phone, such as Miao Miao and Blucon.
Update: The FreeStyle Libre 2 system was launched in November 2020. Libre 2 has all the benefits of the FreeStyle Libre system with an update to accuracy and optional real-time alarms. When you use Libre 2 sensors, the reader will alert the user to the need to perform a scan when their glucose goes out of target range.
How does the Libre system work?
The Libre system includes a sensor (about the size of a £2 coin) which is worn on the back of the upper arm for up to 14 days, and a handset which the user scans over the sensor to obtain a reading. A compatible mobile phone can be used instead of the handset.
The reading also shows:
- your current glucose level
- a graph of your glucose levels over the last 8 hours
- and a trend arrow showing whether the glucose reading is stable, rising or falling
The Libre handset includes a smart FreeStyle Optium blood glucose meter and blood ketone meter. If you have a compatible smart phone you can use the Libre app to scan with your phone instead of the handset.
Diabetes technology manufacturer, Abbott, markets Libre as a replacement for fingerstick blood glucose monitoring, but note that the Abbott FreeStyle Libre UK website says:
“A finger prick test using a blood glucose meter is required
- during times of rapidly changing glucose levels when interstitial fluid glucose levels may not accurately reflect blood glucose levels or
- if hypoglycaemia or impending hypoglycaemia is reported by the System or
- when symptoms do not match the System readings.”
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To find out if you can get flash glucose sensing on the NHS, see our ‘Can I get Libre / Libre 2 on the NHS?‘ page.
Useful publications about flash glucose monitoring (Libre)
Abbott hold regular teaching webinars for Libre users and healthcare professionals, which are free but you must register to take part.
The Edinburgh Centre for Endocrinology & Diabetes has produced a helpful guide to using Libre data to improve glucose control in type 1 diabetes.
NICE Medtech Innovation Briefing (MIB) published in July 2017.
MIBs are Objective information on device and diagnostic technologies to aid local decision-making by clinicians, managers and procurement professionals. The information provided includes a description of the technology, how it’s used and its potential role in the treatment pathway. This is not the same as NICE guidance, and does not have to be acted on by clinicians, managers or commissioners.
The Diabetes Technology Network (part of the Association of British Clinical Diabetologists) has produced a series of helpful videos about making best use of flash glucose monitoring.
The Diabetes Technology Network’s position statement regarding flash glucose monitoring (Libre 1 and 2). Note that NHS England’s reimbursement programme ended in 2021 and there is no longer a set of national criteria. Different areas have their own set of criteria but DTN’s position statement can help you make a good case. Prescriptions for flash sensors have continued to increase since the end of the national guidance so the percentage of people with type 1 who are using flash is continuing to increase.
Libre website & webshop (be sure to tick the VAT exemption box)
To join the chat about Libre, visit the Facebook group.
