The FreeStyle Libre Continuous Glucose Monitor

The FreeStyle Libre system is a continuous glucose monitor (CGM) worn on the upper arm that provides real-time blood glucose (blood sugar) readings every minute for people who have type 1 diabetes or type 2 diabetes, especially those who take insulin.

There are Freestyle Libre systems you can choose from:

  • The original Freestyle Libre 14-day system (approved for adults 18 and older)
  • The Freestyle Libre 2 system (approved for adults and children age 4 and older)
FreeStyle Libre sensor on a patient's arm

navorolphotography / Getty Images

It has been reported that people who frequently test their blood sugar have lower A1C levels (a measure of average glucose levels over two to three months) and steadier glucose levels.

But traditional monitoring requires multiple fingerpricks to draw blood that is then tested every day. This can be time-consuming, inconvenient, and invasive.

CGM devices like the FreeStyle Libre can greatly improve this process.

How the FreeStyle Libre Works

The FreeStyle Libre system uses modern technology to provide real-time glucose readings every minute with a pre-calibrated sensor.

These devices, two among several in a newer generation of CGMs, don't have the bulky transmitter of CGMs past. Instead, they use a small, water-resistant sensor that you insert (using a provided applicator) just under the skin on the back of the arm. This sensor measures interstitial fluid (fluid in the space around your cells), which is comparable to capillary blood.

By scanning your sensor with your Freestyle Libre reader device, your blood glucose reading will be registered and logged. You will be able to view both individual readings and trends over time.

The FreeStyle Libre 2 has alarms to notify you if your glucose levels are too high or two low, but you need to turn them on. Your reader also needs to be within 20 feet of you in order to receive them.

Be aware the original FreeStyle Libre does not have this alarm feature and has not been evaluated for use by people with hypoglycemia unawareness (meaning they are unable to recognize the symptoms of a extreme dip in blood sugar levels).

The Libre can store 90 days' worth of results and be worn for up to 14 days, at which point it stops working and must be disposed of and replaced.

You cannot use the meter to test for ketones.

How Often You Should Scan Your Sensor

After a one-hour startup period, you can retrieve a blood glucose reading instantly by scanning the sensor with your reader or smartphone app. (As of March 2021, the FDA was still reviewing the app for the Freestyle Libre 2, so the reader is still needed for that model.)

You can scan as often as you'd like, but in order to capture all data, it is recommended that you scan your sensor at least once every eight hours.

Studies conducted by Abbott, the maker of the FreeStyle Libre, have demonstrated that people who use this sensor wind up scanning the sensor more often than they would test their blood sugar with a fingerprick, which provides them with more accurate data.

Benefits

The system eliminates fingerpricks for calibration, which translates to less manual effort.

Aside from being more convenient, it is pain-free. This may motivate patients to take their readings more often (or as recommended, if not doing so already)—particularly those who loathe traditional testing.

In addition, large amounts of data and trend reports can help people with diabetes reduce their risk for low blood sugar and help them figure out insulin dosing and meal planning.

This could all lead to better diabetes management.

When Manual Testing May Be Necessary

Inaccuracies sometimes occur with CGMs. In particular, this can happen:

  • During rapid changes in blood glucose, such as after eating, dosing insulin, or exercising
  • With severe dehydration and excessive water loss

Because of this, the Libre's reader also has a blood glucose meter within the system. This allows you to perform a fingerprick and test your blood if you need to double-check that the CGM reading is accurate.

Other cases in which performing a fingerprink test is necessary:

  • If you are using the FreeStyle Libre 14 day system and begin to have symptoms of blood sugar that is too high or too low (as there is no alarm to draw your attention to these readings)
  • When the FreeStyle Libre alerts you that it isn't able to determine where your glucose is trending (you'll see a warning symbol on the reader's screen if this happens)

If you use the original FreeStyle Libre and it detects too-high or too-low blood sugar levels, set a reminder on your reader to scan your sensor again soon (a prompt will appear on the screen).

Availability and Cost

FreeStyle Libre systems are available in pharmacies nationwide with a prescription.

For people who have private insurance or are on Medicaid, the FreeStyle Libre may cost $40 to $75 per month. The device is fully covered by Medicare for those who qualify. Certain patients may be able to take advantage of Abbott's free trial offer.

In addition to the cost of the device, the FreeStyle Libre uses test strips called Precision Neo test strips (for fingerprick testing). Typically, a box of 50 strips costs about $20.

They are individually foil-wrapped so that they can be used until the expiration date. Using other test strips with the built-in meter may produce an error, start a test, or cause it to not turn.

Comparison to Other Devices

The FreeStyle Libre device is referred to as a flash glucose monitoring system. As compared to other CGMs, like the Dexcom G6, the Libre system checks glucose every minute rather than every five minutes and it can be worn for 14 days as opposed to 10.

It is very accurate and does not require fingerprick calibrations. And because the Libre does not require a transmitter, the price for it and its sensors is lower compared to other CGMs.

Whereas other CGMs are approved for belly and buttocks placement, the FreeStyle Libre is only approved for the back of the arm. If placed in other areas, the sensor may not function properly.

Storage

Storage is important for protecting the sensor and keeping the readings as accurate as possible.

The FreeStyle Libre 14-day kit should be stored at a temperature between 39 and 77 degrees F. The FreeStyle Libre 2 kit should be stored at between 36 and 82 degrees F.

Both Libre devices should be kept at a non-condensing humidity of between 10% and 90%. If your refrigerator meets these criteria you can certainly store the kit there.

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Article Sources
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  1. American Diabetes Association. 7. Diabetes technology: standards of medical care in diabetes—2021Dia Care. 2021;44(Supplement 1):S85-S99. doi:10.2337/dc21-S007

  2. Blum A. Freestyle Libre glucose monitoring system. Clin Diabetes. 2018;36(2):203-204. doi:10.2337/cd17-0130

  3. Abbott Laboratories. FreeStyle Libre.

  4. Abbott. FreeStyle Libre 14 Day indications and important safety information. February 2021.

  5. Abbott. FreeStyle Libre: Medicare guide. Updated November 2020.

  6. Centers for Medicare & Medicaid Services. Therapeutic continuous glucose monitors.

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