What is Continuous Glucose Monitoring (CGM)?

CGM systems continuously measure interstitial fluid glucose levels throughout the day and record this info in the reading device.

Our minute to minute glucose monitoring systems, FreeStyle Libre 2 and FreeStyle Libre 3, use a small, discreet and easy to use1 sensors. They provide your patients with real-time glucose readings on their smartphones◊,◊◊ day and night.

CGM vs. Blood Glucose Monitoring

CGM offers various benefits for your patients over Blood Glucose Monitoring

Blood Drop icon

Blood Glucose

Measures glucose levels in blood

  • Requires finger pricks

  • Requires manual testing multiple times a day

  • Requires you to carry strips, lancet and meter to test

  • Provides glucose levels at a single moment of time

FreeStyle Libre 2 sensor icon FreeStyle Libre 3 sensor icon

FreeStyle Libre Portfolio

Measures glucose levels in interstitial fluid

  • Painless2, without finger pricks

  • Automatically measures and updates glucose levels every minute

  • Sensor delivers readings directly to your patients smartphone◊,◊◊,ǁ

  • Provides the whole picture about both the current glucose level and changes over timeφ

  • Continuous glucose levels help to see the impact of activities and food

  • Proven to reduce time in hypoglycaemia2,4 and improve overall glucose control3,4

How does the FreeStyle Libre Portfolio works to provide continuous glucose monitoring?

FreeStyle Libre sensor-based glucose monitoring technology allows people with diabetes to see their glucose levels in real-time.

1. Patients wear the sensor

FreeStyle Libre sensors are small, unobtrusive, and easily applied1 to the back of the upper arm. The sensors come with an applicator and use a small, flexible tip that is inserted just under the skin.

2. Sensor measures glucose levels

The sensor continuously measures glucose readings through the whole 14 day wear period.

3. Patients view glucose readings on their smartphone

Patients who start their sensor using the FreeStyle LibreLink or FreeStyle Libre 3 app◊◊ can see their glucose levels in real-time and receive optional alarms if they are too high or too low.¤

Interstitial fluid vs. 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 children5   
  • 2.4 minutes for adults5

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 sensors in the interstitial fluid, are similar to blood glucose.

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

When blood glucose levels decrease,
the glucose measurement displayed by the FreeStyle Libre sensors 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 continuous glucose monitoring?

FreeStyle Libre 2

The FreeStyle Libre 2 system has an overall MARD of 9.2%5,6

The FreeStyle Libre 2 system has an overall 9.2% MARD with 99.9% of readings in Zones A and B of the Consensus Error Grid without the need for finger prick calibration.

FSL2 Mard

FreeStyle Libre 3

The FreeStyle Libre 3 system has an overall MARD below 8%

  • 7.8% Overall MARD7

  • 93.4% Within ± 20% mg/dl / ± 1.1 mmol/L7

    Percentage of readings within ± 1.1 mmol/L of YSI values for glucose levels < 3.9 mmol/L and ± 20% when ≥ 3.9 mmol/L.

  • 99.9% in Zones A and B of Consensus Error Grid1


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.

The FreeStyle Libre 2 System

Minute-to-minute glucose readings sent to your patient's smartphone to help them manage their diabetes more confidently9

The FreeStyle Libre 3 System

Your patients know sooner can act faster and be ready to avoid hypos with our next-gen continuous glucose monitoring

Digital Health Solutions

Discover how you can get the most out of the FreeStyle Libre Portfolio with our Digital Health Solutions for both you and your patients

References & Disclaimers

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

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

◊ 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 may require 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.

ǁ Glucose readings are automatically displayed in the FreeStyle LibreLink app only when your patients' smartphones and sensors are connected and in range. 

φ For FreeStyle LibreLink and FreeStyle Libre 2 reader users only, users need to scan once every 8 hours for a complete glycaemic picture and during signal loss.

¤ Alarms notifications will only be received when alarms are turned on and the Freestyle Libre 2 sensor is within 20ft unobstructed of the reading device. Users must have override do not disturb settings enabled to receive alarms and alerts on the smartphone. For FreeStyle Libre 3 sensor users the notifications will only be received when alarms are turned on and the sensor is within 33 feet unobstructed of the reading device.

* FreeStyle Libre sensors refers to the FreeStyle Libre 2 and FreeStyle Libre 3 sensors.

1. Data on file, Abbott Diabetes Care, Inc.

2. Haak, T. Diabetes Ther (2017): https://doi.org/10.1007/s13300-016-0223-6.

3. Yaron, M. Diabetes Care (2019): https://doi.org/10.2337/dc18-0166.

4. Leelarathna, L. N Engl J Med. (2022): DOI: 10.1056/NEJMoa2205650.

5. Alva, Shridhara, Timothy Bailey, Ronald L. Brazg, Erwin S. Budiman, Kristin Castorino, Mark P. Christiansen, Gregory Forlenza, Mark Kipnes, David R. Liljenquist, and Hanqing Liu. “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). http://doi.org/10.1177/1932296820958754.

6. FreeStyle Libre 2 system Performance Data Sheet.

7. FreeStyle Libre 3 User Manual. FreeStyle Libre 3 demonstrates 7.8% overall MARD with 7.5% adult MARD and 8.6% paediatric MARD (age 6-17) in accuracy to YSI. 

8. Data on file, Abbott Diabetes Care. Data based on the number of users worldwide for the FreeStyle Libre systems compared to the number of users for other leading personal use sensor-based glucose monitoring system.

9. Fokkert, M. BMJ Open Diab Res Care (2019): https://doi.org/10.1136/bmjdrc-2019-000809