Why Sensor-Based Glucose

Sensor-based glucose monitoring systems continuously measure glucose levels throughout the day without the need for finger pricks

Designed to replace the need for routine finger pricks, a sensor based 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 during 14 days.

Using the FreeStyle LibreLink app, patients can scan their FreeStyle Libre 2 sensor to see their glucose levels.

Patients using a FreeStyle Libre 3 sensor can view their glucose levels using the FreeStyle Libre 3 app*.

Sensor-Based Glucose Monitoring vs Blood Glucose Monitoring

What's the difference between sensor-based 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 skin and not from the blood.

Interstitial Fluid and Blood Glucose Readings

Why don’t interstitial fluid readings and blood glucose readings always match?

Glucose in the blood takes time to make its way into the interstitial fluid so there may be a lag time between the readings.

Average lag time between the FreeStyle Libre sensors^ and blood glucose readings:

       • 2.1 minutes for children4
       • 2.4 minutes for adults4

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

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.

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


How accurate is sensor-based glucose monitoring?

FreeStyle Libre 2 sensors are accurate, stable and consistent over 14 days4 without the need for finger prick calibration.

Accuracy is assessed by looking at the glucose readings the sensor provides compared to 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 two 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.4

Find out about the accuracy of our next generation continuous glucose monitoring system, the FreeStyle Libre 3 system

Consensus Error Grid for the FreeStyle Libre 2 system compared with reference.

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 sensors^ are calibrated at the factory – so your patients won’t need to calibrate it using a finger prick, ever. This means you and your patients can be confident in the accuracy of the system, and that the accuracy you're receiving is what is reported, without being affected by discrepancies caused by finger prick calibration.

FreeStyle Libre Portfolio

FreeStyle Libre 2 System

The Flash Glucose Monitoring system with optional alarms

FreeStyle Libre 3 System

Our next generation of continuous glucose monitoring technology

References & Disclaimers

Images are for illustrative purposes only. Not real patient or data.

† Finger pricks are required if glucose readings do not match symptoms or expectations.

◊ Patients choose which device they want to receive alarms: FreeStyle Libre 2 reader or FreeStyle LibreLink app. They must start their FreeStyle Libre 2 sensor with that selected device. Once the patient scans their FreeStyle Libre 2 sensor with that device, they can receive alarms only on that device. The FreeStyle LibreLink app is only compatible with certain mobile devices and operating systems. Please check the website for more information about device compatibility before using the app. Use of FreeStyle LibreLink requires registration with LibreView.

* The FreeStyle Libre 3 app is only compatible with certain mobile devices and operating systems. Please check our website for more information about device compatibility before using the app. Sharing of glucose data requires registration with LibreView.

φ For a complete glycaemic picture, scan once every 8 hours.

₸ Sensor is water-resistant in up to 1 meter (3 feet) of water. Do not immerse longer than 30 minutes. Not to be used above 10,000 feet.

^ FreeStyle Libre 2 and FreeStyle Libre 3 systems are part of the same family of products.

1. Hortensius, Johanna., et al. Perspectives of patients with type 1 or insulin-treated type 2 diabetes on self-monitoring of blood glucose: a qualitative study. BMC Public Health 12.1 (2012):167.

2. Chudyk, Anna., et al. Self-Monitoring Technologies for type 2 Diabetes and the Prevention of Cardiovascular Complications: Perspectives from End Users. Journal of Diabetes Science and Technology 5.2 (2011): 394–401.

3. Haak, Thomas., et al. Flash glucose-sensing technology as a replacement for blood glucose monitoring for the management of insulin-treated type 2 diabetes: a multicenter, open-label randomized controlled trial. Diabetes Therapy 8.1 (2017): 55-73

4. Alva S, et al. Accuracy of a 14-Day Factory-Calibrated Continuous Glucose Monitoring System With Advanced Algorithm in Pediatric and Adult Population With Diabetes. Journal of Diabetes Science and Technology. September 2020. doi:10.1177/1932296820958754.