FreeStyle Libre 2 is a continuous glucose monitoring (CGM) system that's designed to replace fingersticks and lessen the need for test strips in people with diabetes. It measures your glucose levels every minute throughout the day to better help you manage your blood sugar. The FreeStyle Libre 2 system uses a sensor that's attached to your skin on the back of your upper arm. You can scan the sensor and have the glucose reading displayed on an app in your smartphone (compatible phones only), or the FreeStyle Libre 2 handheld reader. The sensor must be replaced every 14 days, and the sensors require a prescription.
Monitor glucose levels
The FreeStyle Libre 2 system is made up of two parts that work together to measure and record your glucose levels throughout the day.
Sensor: The sensor is attached to the skin on the back of your upper arm to measure your glucose levels from just below the skin.
Reader: The handheld reader displays and stores the readings. You can use the FreeStyle Libre 2 Reader or the FreeStyle Libre 2 app on your smartphone.
Can be used by people ages 4 years and older
Can be used with the FreeStyle Libre 2 Reader or your smartphone
Sensor lasts up to 14 days
Sensor can only be placed on the back of the upper arm
Must wait 60 minutes after placing a new sensor to check glucose
Sensor must be stored between 36°F and 82°F to work properly
How to set up your FreeStyle Libre 2:
You can use either the FreeStyle Libre 2 handheld reader or a separate smart device (e.g., your smartphone) to display and store your glucose readings.
If you're using a smart device, download the FreeStyle Libre 2 app. To connect FreeStyle Libre 2 to a smart device (e.g., a compatible phone), open the app and follow the instructions. Make sure your phone is connected to a WiFi or cellular network.
If you're using the reader from FreeStyle Libre 2, set up FreeStyle Libre 2 to work with your reader with this guide.
How to start using your FreeStyle Libre 2:
When you're ready to apply your FreeStyle Libre 2 sensor, first wash and dry your hands. Choose the place on the back of your upper arm where you want to insert the sensor and wipe the area with an alcohol wipe. Then, remove the sensor from its packaging and push down firmly against your skin to apply it.
When the FreeStyle Libre 2 sensor is on your skin, pull the applicator away from your body. Make sure the sensor is secure. Watch the instructional video to learn more about applying your sensor.
Each time you apply a new FreeStyle Libre 2 sensor, you'll need to wait 1 hour before you can check your glucose readings with the handheld reader or app on your smart device.
If you're using the FreeStyle Libre 2 reader, press the home button to turn it on. Touch "start new sensor" and hold the reader within 1.5 inches from the sensor to scan it.
If you're using a smart device, follow the instructions on the FreeStyle Libre 2 app to scan your sensor and view your glucose reading.
Watch this video to learn more about getting your first reading with the FreeStyle Libre 2.
How to remove FreeStyle Libre 2 sensors:
You'll need to replace your FreeStyle Libre 2 once every 14 days, or sooner if it becomes loose.
To remove the sensor, find the edge of the adhesive on your sensor and pull up on it. Then, slowly peel the sensor off your skin.
When applying a new sensor, choose a place on the back of your upper arm that's different from the most recent position. This will help prevent discomfort.
Screw the used applicator and lid back together and throw it away in a sharps container or yellow biohazard bag. Your used sensors can be wiped down with disinfectant and thrown away as electrical waste, like a battery.
FreeStyle Libre 2 can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
You must remove FreeStyle Libre 2 before getting a magnetic
resonance imaging (MRI), computed tomography (CT) scan, or high-frequency electrical heat (diathermy) treatment. These medical tests might damage the sensor and cause incorrect glucose readings. If you're scheduled for any medical tests or imaging, let your provider know that you're using FreeStyle Libre 2.
If you're going through security, such as at the airport, let the security personnel know that you're wearing a CGM. Don't go through (or put any part of the FreeStyle Libre 2 system through) any body scanners or X-ray machines. Instead, request that they use another method for screening, such as with a hand-wand, visual inspection, or a walk-through metal
detector. It isn't known how X-rays or other scanners affect FreeStyle Libre 2, and they could damage the sensor and affect its performance.
If you have symptoms of low or high blood sugar and they aren't matching up with your FreeStyle Libre 2 readings, always do a fingerstick blood sugar test and contact your provider. If you're using the FreeStyle Libre 2 app, make sure to have a separate blood glucose monitor at home. While the FreeStyle Libre 2 reader has a built-in blood glucose monitor, the app doesn't have one.
FreeStyle Libre 2 has optional alarms that must be turned on in the app or reader if you want to use them. In order for you to get alarms, your reader or phone must be within 20 feet of you at all times. If you're using a smart device, make sure that the Bluetooth setting is on. Keep your reader or device charged and turned on. The alarms won't include your glucose reading, so you'll need to scan your sensor to check your level.
Taking vitamin C (ascorbic acid) can affect the accuracy of the glucose readings from FreeStyle Libre 2. If you take more than 500 mg of vitamin C while wearing the sensor, your glucose readings might be falsely high. This can raise your risk for dangerously low blood sugar levels. Before taking any supplements, check how much vitamin C they contain. Vitamin C is commonly found in multivitamins and cold remedies. If you're not sure, ask your pharmacist for help.
The FreeStyle Libre 2 sensors have an adhesive that keeps them attached to your skin. If you notice redness, swelling, or a lot of irritation around or under your sensor, remove the sensor and contact your healthcare provider.
The FreeStyle Libre 2 sensors are only meant for single use. Don't reuse or share them with anyone else. If you reuse them, you might get inaccurate glucose readings. Reusing or sharing sensors raises the risk of infection. If your sensor becomes loose, remove it and apply a new sensor.
People ages 4 years and older: Place a new FreeStyle Libre 2 sensor on the skin of the back of the upper arm once every 14 days.
Use with automated insulin dosing (AID) systems
Getting magnetic resonance imaging (MRI), computed tomography (CT) scan, or high-frequency electrical heat (diathermy) treatment at the same time
Age 3 years or younger
Currently pregnant
Currently on dialysis
Currently seriously ill
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Heinemann, L., et al. (2020). Benefits and limitations of MARD as a performance parameter for continuous glucose monitoring in the interstitial space. Journal of Diabetes Science and Technology.
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