Flash Glucose Monitoring

Continuously measures glucose levels throughout the day

Designed to replace the need for routine finger pricks for people with diabetes, a flash glucose monitoring system is made up of a sensor that is worn on the back of the upper arm that continuously measures the glucose concentration in the body's interstitial fluid. Using the reader or the FreeStyle LibreLink app people with diabetes scan their FreeStyle Libre 2 sensor to see their glucose levels.


What's the difference between flash glucose monitoring and blood glucose monitoring?

Sensor glucose readings come from the interstitial fluid, a thin layer of fluid that surrounds the cells of the tissue below the skin4 and not from the blood.

Watch the video to find out more about
 the difference between testing interstitial fluid vs blood glucose

Interstitial fluid readings and blood glucose readings don’t always match

Glucose in the blood takes time to make its way into the interstitial fluid so there may be a lag time. The average lag time between Sensor and blood glucose readings is about 2.4 minutes in adults.7

When glucose levels are stable, the two readings may be very similar. However, if glucose is rising or falling, then they might be different.6


When blood glucose levels are stable, the glucose measurement displayed by the FreeStyle Libre systems in the interstitial fluid, are similar to blood glucose.


When blood glucose levels increase, the glucose measurement displayed by the FreeStyle Libre systems in the interstitial fluid may be below the blood glucose reading.


When blood glucose levels decrease, the glucose measurement displayed by the FreeStyle Libre systems in the interstitial fluid may be higher than the blood glucose reading.


The FreeStyle Libre Systems

The FreeStyle Libre systems are the leading sensor glucose monitoring devices globally5 and the only flash glucose monitoring systems in the UK. They consist of a small, discreet sensor worn on the back of the arm with a reader or phone app to scan the sensor. People with diabetes must scan once every 8 hours for a complete glycaemic picture, ensuring they remain engaged with their glucose monitoring throughout the day.

How accurate are the FreeStyle Libre Systems?

The FreeStyle Libre 2 system is accurate, stable and consistent over 14 days7 without the need for fingerprick calibrations.

To assess the accuracy of the FreeStyle Libre 2 sensor, the glucose readings the sensor provides are compared to a known independent reference. In this case the reference is a finger prick blood glucose reading which is taken at the same time as the sensor scan. The comparison between the 2 different readings is plotted on a graph called a Consensus Error grid.

The closer the sensor reading to the reference blood glucose meter reading, the better the accuracy. This is reflected by the Consensus Error Grid by various areas on the graph labelled A to E. The higher the percentage of readings in Zones A and B, the more accurate the sensor is. The consensus Error Grid below shows 99.9% of readings in Zone A + B of the Consensus Error Grid.5

No finger prick calibration ever

Calibration is needed for commercially available CGM systems because the sensitivity of each sensor can vary within each batch that is made. The FreeStyle Libre 2 flash glucose monitoring sensor is calibrated at the factory - so people with diabetes won’t need to calibrate it using a finger prick, ever. This means they can be confident in the accuracy of the system, and they can be confident the accuracy they're receiving is what is reported, without being affected by discrepancies caused by finger prick calibration.

Find out more about flash glucose monitoring and the FreeStyle Libre 2 system in our FreeStyle Academy

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Modal libre bg * Scanning the sensor to obtain glucose values does not require lancets ×
*1. Scanning the sensor to obtain glucose values does not require lancets 2. 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 hypoglycemia or impending hypoglycemia is reported but the symptoms do not match the system readings. ×

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