Flash Vs Continuous Glucose Monitoring

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Type 1 What is the Difference Between Flash and Continuous Glucose Monitoring?

Continuous glucose monitoring (CGM) and flash glucose monitoring (Flash) are two methods that people with diabetes use to automatically track their blood glucose levels day and night. CGM devices transmit data wirelessly to a reader or smartphone. Flash sensors must be scanned with a handheld reader or compatible smartphone. Both are wearable-technology devices that help people with diabetes understand and manage their blood sugar levels.  

What is Continuous Glucose Monitoring? (CGM)

Checking your blood sugar frequently is an important part of diabetes management. A continuous glucose monitoring device is wearable technology that allows you to access your blood sugar levels at a glance – either via a handheld reader or a compatible smartphone.  

Continuous glucose monitoring allows you to access data in real-time or retrospectively. It can be used as a standalone device or as part of an integrated solution with your insulin pump. 

A CGM works by measuring the amount of glucose in your interstitial fluid – the fluid between your cells. Unlike a finger-prick test which is an accurate snapshot of your blood sugar level at a single point in time, the blood glucose reading from your interstitial fluid has a slight delay. 

What is Flash Glucose Monitoring?

Flash glucose monitoring shares many similarities with CGM. Technically it’s a type of continuous glucose monitoring called intermittently scanned CGM, but most often it is simply referred to as Flash. 

Like other CGM devices, Flash is wearable technology that measures your interstitial blood sugar levels day and night. Unlike real-time CGM, the data is not automatically transmitted. You need to scan (or flash) the sensor on your arm using your handheld reader or your smartphone to access your blood sugar level.  

There are only two models of flash glucose monitors available on the market: the Freestyle Libre and Freestyle Libre 2.  

Flash is available on the NHS, but you must be eligible. Alternatively, you can purchase a flash device yourself. The rough cost is: 

  • £115 for a starter pack of a reader and 2 sensors 
  • £50 for a sensor  

How does CGM Work?

A CGM device has three parts: a sensor (worn on the arm or belly), a wireless transmitter and a display device. The display device could be a handheld reader, a mobile phone or even an insulin pump monitor.  

Finger-prick testing done with traditional blood glucose meters only give one snapshot of your blood sugar level. CGM tells you what your current levels are, where they have been and whether they are trending up or down. This allows you to make informed decisions about what action to take, if any. 

One of the most important benefits of CGM is the peace of mind that many users feel. Continuous glucose monitoring gives them a better understanding of their blood sugar patterns and confidence that they can avoid unexpected hypos.   

How does Flash Glucose Monitoring Work?

Flash glucose monitoring works similarly to CGM except that it requires you to scan your sensor to access your blood glucose information. Each time you flash your sensor, you can access the last 8 hours of data (this is helpful to see your overnight levels). To review a full day’s worth of data, you must scan at least once every 8 hours. 

When you scan the sensor, you get your current blood sugar reading and an arrow showing which direction your blood sugar is going. You can also download your results to a computer or other device to look at trends and patterns. Like CGM, Flash measures the blood sugar levels of your interstitial fluid.  

A flash system is made up of two parts: a small sensor about the size of a £2 coin worn on the back of the arm and a reader (either a separate handheld device or your smartphone).

What are the Differences between CGM and Flash Glucose Monitoring?

The chief difference between CGM and flash glucose monitoring is that you must remember to scan your sensor to access your blood sugar levels with Flash.  

With continuous glucose monitors, you can set up alarms to alert you when your blood sugar goes too high or too low. You can programme alarms for the Freestyle Libre 2 as well, but the original Freestyle Libre does not have alarms. 

Another key difference is that Flash is a standalone glucose monitoring system. This means it does not currently integrate with any insulin pumps. CGM devices can either be standalone or paired with compatible insulin pumps. 

Finally, CGM requires that you finger-prick twice per day to calibrate the sensor. Flash does not require calibration. 

Which Blood Glucose Monitoring System is Right for Me?

If you are trying to decide if either CGM or Flash is right for you, you should consider the following factors when evaluating a glucose monitoring solution: 

  • Data access – Both CGM and Flash allow you to download your information, share your results and see long-term trends and patterns. However, Flash requires that you scan your sensor at least every 8 hours to ensure uninterrupted access to your data. 
  • Integration with an insulin pump – If you would like to integrate your glucose monitoring with an existing insulin pump or potentially use one in the future, you should speak to your doctor about which CGM devices would be most suitable.  
  • Cost-effectiveness – Both CGM and Flash are more expensive than finger-prick testing alone. However, Flash is more cost-effective than real-time CGM.  
  • NHS eligibility – There are different eligibility criteria for receiving CGM and Flash on the NHS.  

You should always speak to your doctor about what system will best help you achieve your blood sugar goals.   

Flash vs. CGM: A Summary

The biggest benefit of using CGM or Flash is gaining better insight into your blood glucose levels so you can adjust your strategies for better glucose management. For people living with diabetes, these solutions mean fewer finger-prick testing, more insight and more peace of mind.  

However, it can feel overwhelming to determine which blood glucose monitoring system is best for you and if you are eligible for a system on the NHS. At the London Diabetes Centre, we work with our patients to find the right glucose monitoring solution for them.  

Get in touch today to speak to a member of our expert team about continuous glucose monitoring.  

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Carol Willis

Carol Willis - Diabetes Clinic Facilitator

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